(4) A man starts walking north at 4 ft/s from a point P. Five minutes later a woman starts walking south at 5 ft/s from a point 500 ft due east of P. At what rate are the people moving apart 15 min after the woman starts walking? (5) A ballon is rising at a constant speed of 5 ft/s. A girl is cycling along a straight road at a speed of 15 ft/s. When she passes under the balloon, it is 45 ft above her. How fast is the distance between the girl and the balloon increasing after 3 s later?