Harvey, Laura, and Gina take turns throwing spit-wads at a target. Harvey hits the target 1/2 the…

Harvey, Laura, and Gina take turns throwing spit-wads at a target. Harvey hits the target 1/2 the time, Laura hits it 1/3 of the time, and Gina hits the target 1/4 of the time. Given that somebody hit the target, what is the probability that it was Laura?