I don't know how to solve it. Can you explain why?

Mr. R. Hood is a good archer. He can regularly hit a target having a 3-ft. diameter and often hits target's bull's-eye, which is 0.5 ft. diameter from 50 ft. away. Suppose the miss is measured as the radial distance r from the center of the target and, furthermore, that the radial miss distance R is a Rayleigh random variable with pdf fR(r) = (r14) exp( r2 [8] u(r), where u(r) is a unit step function. (a) Determine the probability of Mr. Hood hitting the target. (b) Determine the probability of Mr. Hood hitting the bull' -eye. (c) Determine the probability of Mr. Hood hitting the bull'seye given that he hits the target. Answers: (a) 0.2452, (1)) 0.0078, and ((2) 0.0317