input: Write a python function to calculate compound interest.
  assert compoundInterest(1000, 5, 5) == 1276.2815625000003
  assert compoundInterest(1500, 4.3, 6) == 1938.8368221341054
  assert compoundInterest(2000, 3, 10) == 2687.204708940679
output: def compoundInterest(principal, rate, time):
      return principal * (1 + rate / 100) ** time