A = {0, 1, -3, 6, -8, -10}
B = {-1, 2, -4, 7, 6, -9}
If a is a number that is randomly selected from Set A, and b is a number that is randomly selected from Set B, what is the probability that ab < 0? Options:
A) 1 / 4  B) 1 / 3  C) 5 / 13  D) 5 / 12  E) 1 / 2

Rationale: for the product of 2 numbers to be negative either of them must be positive or negative : p ( positive , negative ) = 2 / 6 * 3 / 6 = 6 / 36 ; p ( negative , positive ) = 3 / 6 * 3 / 6 = 9 / 36 p = 6 / 36 + 9 / 36 p = 15 / 36 p = 5 / 12 answer : d
Answer: D