Let X denote the reaction time, in seconds, to a certain stimulus and Y denote the temperature (F) at which a certain reaction starts to take place. Suppose that two random variables X and Y have the joint density f(x, y) = 4xy 0 if 0 < x Y). -x "LL 1. II. III. So Lo So L 1 1 4xy dydx 4xy dydx 4xy dydx 1-y IV. Arydzdy So So Oll O III O IV