Given that a and b are real numbers such that -3 ≤ a ≤ 2 and -1 ≤ b ≤ 4, and values for a and b are chosen at random, what is the probability that product a*b is positive?
Here is a graph. The probability is the area of the shaded region over the area of the total region [ABCD].
Can you solve it with this picture?