OfficeMax. com sells pencils to individuals and to organizations such as schools or businesses. For up to ten boxes of pencils, they cost $1.97 per box and $3 shipping and handling. If a school wants to order more than 10 and less than 50 boxes of pencils, they get a 10% discount and must pay $10 shipping and handling. If an organization buys 50 boxes or more, they get free shipping and get a 12% discount. If we have to program the website to give customers a subtotal, what equation can we use?