Help needed and thanks in advance !!!!

(c) (20 marks) The number of people who enter a pizzeria in a period of 15 minutes is a non-negative random variable k with known moment gener- ating function Mp(t) = E(et ). Each person who comes in buys a pizza. There are n types of pizzas, and each person is equally likely to choose any type of pizza, independently of what anyone else chooses. Give a formula, in terms of My(.), for the expected number of all the different types of pizzas ordered