input: from typing import List
  
  def determine_commission_rate(gross_sales: List[float]) -> float:
      """ Determine the commission rate based on the gross sales amount.
      >>> determine_commission_rate(12000)
      0.1
      >>> determine_commission_rate(7500)
      0.07
      >>> determine_commission_rate(3000)
      0.05
      """
      if gross_sales >= 10000:
          return 0.1
      elif gross_sales >= 5000:
          return 0.07
      else:
          return 0.05
output:     
      total_sales = sum(gross_sales)
      if total_sales >= 10000:
          return 0.1
      elif total_sales >= 5000:
          return 0.07
      else:
          return 0.05
  