input: Write a function to optimize the given Python code snippet by improving its efficiency. The function should return the appropriate commission rate based on the value of gross_sales.
  
  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(7000)==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