input: Write a python function to calculate interest rate based on principal, rate, and period.
  assert calculate_interest_rate(2000, 4.5, 5) == 450.0
  assert calculate_interest_rate(1000, 3.0, 4) == 120.0
  assert calculate_interest_rate(1500, 5.0, 3) == 225.0
output: def calculate_interest_rate(principal, rate, period):
      return (principal * rate * period) / 100