The general addition rule for two events is presented in Formula 5.3 on page 204 and that

Question:

The general addition rule for two events is presented in Formula 5.3 on page 204 and that for three events is displayed on page 206.
The General Addition Rule
If A and B are any two events, then
P(A or B) = P(A) + P(B) − P(A & B).
a. Verify the general addition rule for three events.
b. Write the general addition rule for four events and explain your reasoning.