Each rear tire on an experimental airplane is supposed to be filled to a pressure of 40 pounds per square inch (psi). let x denote the actual air pressure for the right tire and y denote the actual air pressure for the left tire. suppose that x and y are random variables with the joint density function f(x, y) = k(x2 + y2), 30 ≤ x < 50, 30 ≤ y < 50, 0, elsewhere. (a) find k. (b) find p(30 ≤ x ≤ 40 and 40 ≤y < 50). (c) find the probability that both tires are underfilled