Solve the Problem $n ( A ) = 25 , n ( A \cup B ) = 73$

Multiple Choice

Solve the problem.
-If $n ( A ) = 25 , n ( A \cup B ) = 73$ , and $n ( A \cap B ) = 21$ , find $n ( B )$ .

A) 69
B) 68
C) 48
D) 70