How much survives a round trip

mediumfinanceJavaScript

Money changes from currency A to B to C, and the rates are given in basis points per leg. Find what is left in the end.

Each leg multiplies by its basis-point rate and divides by 10000.
The whole trip is combined into one integer division: amount × a × b ÷ (10000 × 10000).
The numbers stay small enough that no 32-bit value overflows.

exchangeRoundTrip(amountMinor: int, rateABbps: int, rateBCbps: int) → int

Where you start

function exchangeRoundTrip(amountMinor, rateABbps, rateBCbps) {
  
}

Multiply all three factors, then divide once by a hundred million.

Reference solution in JavaScript

function exchangeRoundTrip(amountMinor, rateABbps, rateBCbps) {
  return Math.floor((amountMinor * rateABbps * rateBCbps) / (10000 * 10000));
}