There are 5 pairs of khaki pants, 11 pairs of jeans, 1 pair of gray pants, 6 pairs of black pants, and 2 pairs of red jeans in the closet. What is the probability of randomly picking a gray pair of pants, putting it back, and then randomly choosing a black pair of pants?

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