A trough is 16 ft long and its ends have the shape of isosceles triangles that are 5 ft across at the top and have a height of 1 ft.

A trough is 16 ft long and its ends have the shape of isosceles triangles that are 5 ft across at the top and have a height of 1 ft. If the trough is being filled with water at a rate of 13 ft 3 /min, how fast is the water level rising when the water is 4 inches deep?