Q: If a parachutist lands at a random point on a line between markers A and B, find the probability that she is closer to A than to B. Find the probability that her distance to A is more than three times her distance to B.

A: The first part was simple, but I am having trouble finding a numerical value for the second part. Is this set up correct?

$\displaystyle P(Y\geq\\3A)=\int_{3A}^{B}\frac{1}{B-A}dy$

Thanks.