## A racing problem....

Bob and Al are racing. Their pdfs are given as:

Al 1<= A <=3
Bob 2<=B<=4

What is the probability of Al winning the race? (assuming lesser value means win). I think this is a joint pdf problem and tried using double integral on both of them:
int(2,4) int(2,B) A*B...not sure if the equation is right though....any help?
thanks