diff --git a/common/calculate-multi.ts b/common/calculate-multi.ts
deleted file mode 100644
index 5ff23cdb..00000000
--- a/common/calculate-multi.ts
+++ /dev/null
@@ -1,27 +0,0 @@
-import * as _ from 'lodash'
-
-export function getMultiProbability(
-  totalShares: {
-    [answerId: string]: number
-  },
-  answerId: string
-) {
-  const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
-  const shares = totalShares[answerId] ?? 0
-  return shares ** 2 / squareSum
-}
-
-export function calculateMultiShares(
-  totalShares: {
-    [answerId: string]: number
-  },
-  bet: number,
-  betChoice: string
-) {
-  const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
-  const shares = totalShares[betChoice] ?? 0
-
-  const c = 2 * bet * Math.sqrt(squareSum)
-
-  return Math.sqrt(bet ** 2 + shares ** 2 + c) - shares
-}
diff --git a/common/calculate.ts b/common/calculate.ts
index fbbfd66f..eeec5251 100644
--- a/common/calculate.ts
+++ b/common/calculate.ts
@@ -1,39 +1,51 @@
+import _ from 'lodash'
 import { Bet } from './bet'
 import { Contract } from './contract'
 import { FEES } from './fees'
 
 export function getProbability(totalShares: { YES: number; NO: number }) {
-  const { YES: y, NO: n } = totalShares
-  return y ** 2 / (y ** 2 + n ** 2)
+  return getOutcomeProbability(totalShares, 'YES')
+}
+
+export function getOutcomeProbability(
+  totalShares: {
+    [outcome: string]: number
+  },
+  outcome: string
+) {
+  const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
+  const shares = totalShares[outcome] ?? 0
+  return shares ** 2 / squareSum
 }
 
 export function getProbabilityAfterBet(
-  totalShares: { YES: number; NO: number },
-  outcome: 'YES' | 'NO',
+  totalShares: {
+    [outcome: string]: number
+  },
+  outcome: string,
   bet: number
 ) {
   const shares = calculateShares(totalShares, bet, outcome)
 
-  const [YES, NO] =
-    outcome === 'YES'
-      ? [totalShares.YES + shares, totalShares.NO]
-      : [totalShares.YES, totalShares.NO + shares]
+  const prevShares = totalShares[outcome] ?? 0
+  const newTotalShares = { ...totalShares, outcome: prevShares + shares }
 
-  return getProbability({ YES, NO })
+  return getOutcomeProbability(newTotalShares, outcome)
 }
 
 export function calculateShares(
-  totalShares: { YES: number; NO: number },
+  totalShares: {
+    [outcome: string]: number
+  },
   bet: number,
-  betChoice: 'YES' | 'NO'
+  betChoice: string
 ) {
-  const [yesShares, noShares] = [totalShares.YES, totalShares.NO]
+  const squareSum = _.sumBy(Object.values(totalShares), (shares) => shares ** 2)
+  const shares = totalShares[betChoice] ?? 0
 
-  const c = 2 * bet * Math.sqrt(yesShares ** 2 + noShares ** 2)
+  const c = 2 * bet * Math.sqrt(squareSum)
 
-  return betChoice === 'YES'
-    ? Math.sqrt(bet ** 2 + yesShares ** 2 + c) - yesShares
-    : Math.sqrt(bet ** 2 + noShares ** 2 + c) - noShares
+  return Math.sqrt(bet ** 2 + shares ** 2 + c) - shares
 }
 
 export function calculateEstimatedWinnings(
@@ -128,15 +140,15 @@ export function calculateCancelPayout(contract: Contract, bet: Bet) {
 export function calculateStandardPayout(
   contract: Contract,
   bet: Bet,
-  outcome: 'YES' | 'NO'
+  outcome: string
 ) {
   const { amount, outcome: betOutcome, shares } = bet
   if (betOutcome !== outcome) return 0
 
   const { totalShares, totalBets, phantomShares } = contract
-  if (totalShares[outcome] === 0) return 0
+  if (!totalShares[outcome]) return 0
 
-  const truePool = contract.pool.YES + contract.pool.NO
+  const truePool = _.sum(Object.values(totalShares))
 
   if (totalBets[outcome] >= truePool)
     return (amount / totalBets[outcome]) * truePool
diff --git a/common/new-bet.ts b/common/new-bet.ts
index 5b23c84e..67f1e90a 100644
--- a/common/new-bet.ts
+++ b/common/new-bet.ts
@@ -1,6 +1,9 @@
 import { Bet } from './bet'
-import { calculateShares, getProbability } from './calculate'
-import { calculateMultiShares, getMultiProbability } from './calculate-multi'
+import {
+  calculateShares,
+  getProbability,
+  getOutcomeProbability,
+} from './calculate'
 import { Contract } from './contract'
 import { User } from './user'
 
@@ -66,7 +69,7 @@ export const getNewMultiBetInfo = (
   const prevOutcomePool = pool[outcome] ?? 0
   const newPool = { ...pool, outcome: prevOutcomePool + amount }
 
-  const shares = calculateMultiShares(contract.totalShares, amount, outcome)
+  const shares = calculateShares(contract.totalShares, amount, outcome)
 
   const prevShares = totalShares[outcome] ?? 0
   const newTotalShares = { ...totalShares, outcome: prevShares + shares }
@@ -74,8 +77,8 @@ export const getNewMultiBetInfo = (
   const prevTotalBets = totalBets[outcome] ?? 0
   const newTotalBets = { ...totalBets, outcome: prevTotalBets + amount }
 
-  const probBefore = getMultiProbability(totalShares, outcome)
-  const probAfter = getMultiProbability(newTotalShares, outcome)
+  const probBefore = getOutcomeProbability(totalShares, outcome)
+  const probAfter = getOutcomeProbability(newTotalShares, outcome)
 
   const newBet: Bet<'MULTI'> = {
     id: newBetId,
diff --git a/web/components/answers-panel.tsx b/web/components/answers-panel.tsx
index 3745bced..771be5be 100644
--- a/web/components/answers-panel.tsx
+++ b/web/components/answers-panel.tsx
@@ -1,18 +1,32 @@
 import clsx from 'clsx'
-import { useState } from 'react'
+import { useEffect, useRef, useState } from 'react'
 import Textarea from 'react-expanding-textarea'
 
 import { Answer } from '../../common/answer'
 import { Contract } from '../../common/contract'
 import { AmountInput } from './amount-input'
 import { Col } from './layout/col'
-import { createAnswer } from '../lib/firebase/api-call'
+import { createAnswer, placeBet } from '../lib/firebase/api-call'
 import { Row } from './layout/row'
 import { Avatar } from './avatar'
 import { SiteLink } from './site-link'
 import { DateTimeTooltip } from './datetime-tooltip'
 import dayjs from 'dayjs'
 import { BuyButton } from './yes-no-selector'
+import { Spacer } from './layout/spacer'
+import {
+  formatMoney,
+  formatPercent,
+  formatWithCommas,
+} from '../../common/util/format'
+import { InfoTooltip } from './info-tooltip'
+import { useUser } from '../hooks/use-user'
+import {
+  getProbabilityAfterBet,
+  getOutcomeProbability,
+  calculateShares,
+} from '../../common/calculate'
+import { firebaseLogin } from '../lib/firebase/users'
 
 export function AnswersPanel(props: {
   contract: Contract<'MULTI'>
@@ -36,33 +50,188 @@ function AnswerItem(props: { answer: Answer; contract: Contract<'MULTI'> }) {
 
   const createdDate = dayjs(createdTime).format('MMM D')
 
+  const [isBetting, setIsBetting] = useState(false)
+
   return (
-    <Col className="p-2 sm:flex-row">
-      <Col className="gap-2 flex-1">
-        <div>{answer.text}</div>
+    <Col>
+      <Col className="p-2 sm:flex-row">
+        <Col className="gap-2 flex-1">
+          <div>{answer.text}</div>
 
-        <Row className="text-gray-500 text-sm gap-2 items-center">
-          <SiteLink className="relative" href={`/${username}`}>
-            <Row className="items-center gap-2">
-              <Avatar avatarUrl={avatarUrl} size={6} />
-              <div className="truncate">{name}</div>
-            </Row>
-          </SiteLink>
+          <Row className="text-gray-500 text-sm gap-2 items-center">
+            <SiteLink className="relative" href={`/${username}`}>
+              <Row className="items-center gap-2">
+                <Avatar avatarUrl={avatarUrl} size={6} />
+                <div className="truncate">{name}</div>
+              </Row>
+            </SiteLink>
 
-          <div className="">•</div>
+            <div className="">•</div>
 
-          <div className="whitespace-nowrap">
-            <DateTimeTooltip text="" time={contract.createdTime}>
-              {createdDate}
-            </DateTimeTooltip>
-          </div>
-        </Row>
+            <div className="whitespace-nowrap">
+              <DateTimeTooltip text="" time={contract.createdTime}>
+                {createdDate}
+              </DateTimeTooltip>
+            </div>
+          </Row>
+        </Col>
+
+        <BuyButton
+          className="justify-end self-end flex-initial"
+          onClick={() => {
+            setIsBetting(true)
+          }}
+        />
       </Col>
 
-      <BuyButton
-        className="justify-end self-end flex-initial"
-        onClick={() => {}}
-      />
+      {isBetting && <AnswerBetPanel answer={answer} contract={contract} />}
+    </Col>
+  )
+}
+
+function AnswerBetPanel(props: {
+  answer: Answer
+  contract: Contract<'MULTI'>
+}) {
+  const { answer, contract } = props
+  const { id: answerId } = answer
+
+  const user = useUser()
+  const [betAmount, setBetAmount] = useState<number | undefined>(undefined)
+
+  const [error, setError] = useState<string | undefined>()
+  const [isSubmitting, setIsSubmitting] = useState(false)
+  const [wasSubmitted, setWasSubmitted] = useState(false)
+
+  const inputRef = useRef<HTMLElement>(null)
+  useEffect(() => {
+    inputRef.current && inputRef.current.focus()
+  }, [])
+
+  function onBetChange(newAmount: number | undefined) {
+    setWasSubmitted(false)
+    setBetAmount(newAmount)
+  }
+
+  async function submitBet() {
+    if (!user || !betAmount) return
+
+    if (user.balance < betAmount) {
+      setError('Insufficient balance')
+      return
+    }
+
+    setError(undefined)
+    setIsSubmitting(true)
+
+    const result = await placeBet({
+      amount: betAmount,
+      outcome: answerId,
+      contractId: contract.id,
+    }).then((r) => r.data as any)
+
+    console.log('placed bet. Result:', result)
+
+    if (result?.status === 'success') {
+      setIsSubmitting(false)
+      setWasSubmitted(true)
+      setBetAmount(undefined)
+    } else {
+      setError(result?.error || 'Error placing bet')
+      setIsSubmitting(false)
+    }
+  }
+
+  const betDisabled = isSubmitting || !betAmount || error
+
+  const initialProb = getOutcomeProbability(contract.totalShares, answer.id)
+
+  const resultProb = getProbabilityAfterBet(
+    contract.totalShares,
+    answerId,
+    betAmount ?? 0
+  )
+
+  const shares = calculateShares(contract.totalShares, betAmount ?? 0, answerId)
+
+  const currentPayout = betAmount
+    ? 0
+    : // calculatePayoutAfterCorrectBet(contract, {
+      //     outcome: answerId,
+      //     amount: betAmount,
+      //     shares,
+      //   } as Bet)
+      0
+
+  const currentReturn = betAmount ? (currentPayout - betAmount) / betAmount : 0
+  const currentReturnPercent = (currentReturn * 100).toFixed() + '%'
+
+  return (
+    <Col className="items-center">
+      <Col className="p-2 items-start">
+        <div className="my-3 text-left text-sm text-gray-500">Amount </div>
+        <AmountInput
+          inputClassName="w-full"
+          amount={betAmount}
+          onChange={onBetChange}
+          error={error}
+          setError={setError}
+          disabled={isSubmitting}
+          inputRef={inputRef}
+        />
+
+        <Spacer h={4} />
+
+        <div className="mt-2 mb-1 text-sm text-gray-500">
+          Implied probability
+        </div>
+        <Row>
+          <div>{formatPercent(initialProb)}</div>
+          <div className="mx-2">→</div>
+          <div>{formatPercent(resultProb)}</div>
+        </Row>
+
+        <Spacer h={4} />
+
+        <Row className="mt-2 mb-1 items-center gap-2 text-sm text-gray-500">
+          Potential payout
+          <InfoTooltip
+            text={`Current payout for ${formatWithCommas(
+              shares
+            )} / ${formatWithCommas(
+              shares + contract.totalShares[answerId]
+            )} shares`}
+          />
+        </Row>
+        <div>
+          {formatMoney(currentPayout)}
+          &nbsp; <span>(+{currentReturnPercent})</span>
+        </div>
+
+        <Spacer h={6} />
+
+        {user ? (
+          <button
+            className={clsx(
+              'btn',
+              betDisabled ? 'btn-disabled' : 'btn-primary',
+              isSubmitting ? 'loading' : ''
+            )}
+            onClick={betDisabled ? undefined : submitBet}
+          >
+            {isSubmitting ? 'Submitting...' : 'Submit trade'}
+          </button>
+        ) : (
+          <button
+            className="btn mt-4 whitespace-nowrap border-none bg-gradient-to-r from-teal-500 to-green-500 px-10 text-lg font-medium normal-case hover:from-teal-600 hover:to-green-600"
+            onClick={firebaseLogin}
+          >
+            Sign in to trade!
+          </button>
+        )}
+
+        {wasSubmitted && <div className="mt-4">Trade submitted!</div>}
+      </Col>
     </Col>
   )
 }