input: Write a function to improve the efficiency of the given Python code snippet.
  
  def determine_commission_rate(gross_sales):
      if gross_sales >= 10000:
          return 0.1
      elif gross_sales >= 5000:
          return 0.07
      else:
          return 0.05
  
  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
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