The probability that event B occurs is 0.6, and the probability that events A and B both occur is 0.25. If the probability that either event A or event B occurs is 0.4, what is the probability that event A will occur?	Choose the correct answer
A) 0.05 B) 0.15 C) 0.45 D) 0.5 E) 0.55

Rationale: p ( a or b ) = p ( a ) + p ( b ) - p ( a n b ) 0.4 = 0.6 + p ( a ) - 0.25 p ( a ) = 0.05 ans : a
Answer: A