A water trough is 30 ft. long and cross-section has the shape of an isosceles trapezoid with 10 in. Wide at the bottom, 25 in. wide at the top, and has a height 15 in. How fast, in in/min, is the water level raising when the trough is being filled with water at the rate of 1.9 ft^3 / min and the water is 9 in. deep?