A pizza shop has 18 different toppings to choose from. Today's special comes with a choice of 5 toppings, plus a choice of 3 types of crust: thin crust, regular, and deep-dish crust. How many different combinations can be made with 5 toppings and 3 crusts?
a. 25,704
b. 203,490
c. 8568
d. 270