input: Write a function to make the following Python code snippet more efficient. 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 and less than 10000, the commission rate is 0.07. If the gross sales are less than 5000, the commission rate is 0.05.
  
  def determine_commission_rate(gross_sales):
      if gross_sales >= 10000:
          commission_rate = 0.1
      elif gross_sales >= 5000 and gross_sales < 10000:
          commission_rate = 0.07
      elif gross_sales < 5000:
          commission_rate = 0.05
      return commission_rate
  
  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(5000)==0.07
  assert determine_commission_rate(10000)==0.1
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