function calculate(item, price1to4, price5to9, price10plus)
{
  input_item = "input_"+item
  output_item = "output_"+item
  quantity = document.getElementById(input_item).value
  
  if (quantity < 5) {
	  result = price1to4*quantity
	}
  if (quantity < 10 && quantity > 4) {
		result = price5to9*quantity
	}
  if (quantity > 9) {
		result = price10plus*quantity
	}

	document.getElementById(output_item).value=result.toFixed(2)
	
}