Tony uses 1/8 cup mozzarella cheese for every 16 square inches of pizza. How much mozzarella will he use for a circular pizza with a diameter of 20 inches?

(A) about 2.5 cups
(B) about 5 cups
(C) about 4 cups
(D) about 6.5 cups

I need an answer with a step by step solution! >_