Winners from last weeks math problem, and the new problem of the week

Pizza! Pizza!

Tony’s Pizzeria sells three sizes of pizzas: small, medium and large.  At Tony’s a small pizza is 10 inches, has four slices and costs $9.95; a medium is 14 inches, has six slices and costs $12.95; and a large is 16 inches, has eight slices and costs $15.95.

Mrs. Smith is ordering pizza for her class.  She asks each student how many pieces of pizza they will eat and discovers a total of 35 slices are needed to feed the entire class.  She decides to call and order from Tony’s Pizzeria.  She must order enough to have at least 35 slices, but having extra slices is fine. How many pizzas of each size should she order in order to minimize cost?