X and Y are modeled inflation rates, in terms of %, for two different countries at the end of a five-year period. X is uniformly distributed on the interval (0, 10). Y, given X = x, is uniformly distributed on the interval (0, x). Calculate Cov(X, Y).

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters