Acrawling tractor sprinkler is
located as pictured below, 100 feet south of a
sidewalk. once the water is turned on, the
sprinkler waters a circular disc of radius 20
feet and moves north along the hose at the rate
of 1/2 inch/second. the hose is perpendicular
to the 10 ft. wide sidewalk. assume there is
grass on both sides of the sidewalk.