input: Write a function to improve the efficiency of the given Python code snippet for determining the commission rate based on gross sales. The function should return the commission rate directly in each conditional block.
  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
      elif gross_sales >= 3000:
          return 0.05
      else:
          return 0