A man starts walking north at 5 ft/s from a point P. Five minutes later a woman starts walking south at 3 ft/s from a point 100 ft due east of point P. At what rate are the people moving apart 15 minutes after the woman starts walking

A man starts walking north at 5 ft/s from a point P. Five minutes later a woman starts walking south at 3 ft/s from a point 100 ft due east of point P. At what rate are the people moving apart 15 minutes after the woman starts walking?