The probability of two events A and B are0.25 and 0.40 respectively. The probability that both A and B occur is 0.15. The probability that neither A nor B occur is _________
Choose the correct option:  A) 0.45  B) 0.4  C) 0.5  D) 0.05  E) 0.6

Rationale: "we are apply that formula . . . . . . . . . . . . . . p ( aorb ) = p ( a ) + p ( b ) - p ( a and b ) = . 25 + . 40 - . 15 = . 50 but the probability of neither a nor b = 1 - . 50 = 0.50 answer : c"
Answer: C