input: Write a function to determine the commission rate based on the gross sales amount. If the gross sales are greater than or equal to 10000, the commission rate is 0.1. If the gross sales are greater than or equal to 5000 but less than 10000, the commission rate is 0.07. For all other cases, where the gross sales are less than 5000, the commission rate is 0.05. Return the corresponding commission rate as a float.
  assert determine_commission_rate(12000)==0.1
  assert determine_commission_rate(7500)==0.07
  assert determine_commission_rate(4500)==0.05
  assert determine_commission_rate(10000)==0.1
  assert determine_commission_rate(5000)==0.07
  assert determine_commission_rate(0)==0.05
output: def determine_commission_rate(gross_sales):
      if gross_sales >= 10000:
          return 0.1
      elif gross_sales >= 5000:
          return 0.07
      else:
          return 0.05