I don't understand what this problem is asking. Anyone know?

Suppose that there is a sample space with five equally likely experimental outcomes: E1, E2, E3, E4, and E5.

Let:

A = {E1, E2}

B = {E3, E4}

C = {E2, E3, E5}

1. Find P(A), P(B), and P(C).

2. Find P(A U B). Are A and B mutually exlusive?