function sumAndMultiply(a, b, c) {
  let add = sum(a,b)[0] + c;
  let product = multiply(a,b)[0] * c;

  return [add,product,`${a} and ${b} and ${c} sum to ${add}.`,`The product of ${a} and ${b} and ${c} is ${product}.`]
}

testSumAndMultiply(4,7,5);