input: Write a function to calculate compound interest given the initial investment amount, the rate of interest per period, and the number of periods. The function should return the compound interest. If the given inputs are invalid, return None.
  def compoundInterest(investment_amount, rate_of_interest, time):
      if investment_amount < 0 or rate_of_interest < 0 or time < 0:
          return None
      compound_interest = investment_amount * (pow((1 + rate_of_interest / 100), time))
      return compound_interest
  
  assert compoundInterest(1000, 5, 5) == 1276.2815625000003
  assert compoundInterest(2000, 3.5, 7) == 2577.340975342649
  assert compoundInterest(500, 0, 2) == 500.0
  assert compoundInterest(800, -1, 4) == None
  assert compoundInterest(-1000, 5, 10) == None
output: def compoundInterest(investment_amount, rate_of_interest, time):
      if investment_amount < 0 or rate_of_interest < 0 or time < 0:
          return None
      compound_interest = investment_amount * (pow((1 + rate_of_interest / 100), time))
      return compound_interest