A.
const complexNumberMultiply = (a, b) => {
const arrayA = a.slice(0, a.length - 1).split("+");
const arrayB = b.slice(0, b.length - 1).split("+");
const aFirst = Number(arrayA[0]);
const aSecond = Number(arrayA[1]);
const bFirst = Number(arrayB[0]);
const bSecond = Number(arrayB[1]);
const resultFirst = (aFirst * bFirst) - (aSecond * bSecond);
const resultSecond = (aSecond * bFirst) + (aFirst * bSecond)
return `${resultFirst}+${resultSecond}i`
}