input: Write a python function to calculate the total cost including tax.
  assert calculate_total_cost(22, 5) == 23.1
  assert calculate_total_cost(100, 10) == 110.0
  assert calculate_total_cost(50, 20) == 60.0
output: def calculate_total_cost(price, tax_rate):
      return price + (price * tax_rate / 100)