A bank operates both a drive-up facility and a walk-up window. On a randomly selected day, let X be the proportion of time that the drive-up facility is in use (at least one customer is being served or waiting to be served) and Y be the proportion of time that the walk- up window is in use. The joint PDF is fxx(x, y) 6 == (x + y) What is the probability that neither window is busy more than one-quarter of the time? What is fx(x)? What is fy(y)?