t 42. Emptying a water trough A water trough has a semicircular cross section with a radius of 0.25 m and a length of 3 m (see figure). a. How much work is required to pump the water out of the trough (to the level of the top of the trough) when it is full? b. If the length is doubled, is the required work doubled? Explain. c. If the radius is doubled, is the required work doubled? Explain. 3 m n 0.25 m