As the problem is worded, there is NO a unique answer.
There are infinitely many possibilities for P(B).
The only thing that we can state certainly is this inequality
0 <= P(B) <= 0.25.
In order for to state that P(B) = 0.25, the problem MUST say in addition that
A and B are mutually COMPLEMENTARY events - but the problem DOES NOT state it.
Ignore the response by @MathLover1, since it is INCORRECT.