input: Write a function that improves the efficiency of a given commission rate determination function based on gross sales. If the gross sales are 10000 or more, the function should return 0.1 as the commission rate. If the gross sales are between 5000 and 9999, the function should return 0.07. For gross sales below 5000, the function should return 0.05. The function should be named determine_commission_rate and should take one parameter, gross_sales.
  assert determine_commission_rate(12000)==0.1
  assert determine_commission_rate(7500)==0.07
  assert determine_commission_rate(4000)==0.05
  assert determine_commission_rate(10000)==0.1
  assert determine_commission_rate(5000)==0.07
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