Chapter 7.3, Problem 34E

In Problems 33 and 34, discuss the validity of each statement. If the statement is always true, explain why. If not, give a counterexample.

$\left(\text{A}\right)$ If $A\text{ or }B$ are disjoint, then $n\left(A\cap B\right)=n\left(A\right)+n\left(B\right)$.

$\left(\text{B}\right)$ If $n\left(A\cup B\right)=n\left(A\right)+n\left(B\right)$, then $A\text{ or }B$ are disjoint.