The question states that n(A) = 5, which means that there are 5 elements in set A. The value of n(B) is asked. Since no information is given about the relationship between sets A and B, we cannot determine the exact value of n(B). However, since the options given are 10, 4, 5, and 25, the most logical choice would be (3) 5, as it is the same value as n(A).