13) Choose the correct answer.

Which situation represents a proportional relationship?

a) the total cost of purchasing unlimited pizza slices for $9.99 at a buffet-style restaurant

B) the total cost of purchasing dress hats for $24.95 each and a hat box for $9.99

C) the total cost of purchasing coordinated T-shirts and shorts for $19.50 per outfit

D) the total cost of buying DVDs for $15.95 each plus a shipping fee of $6.75