Please answer this question for me. This is for an intro course to gas dynamics but this question seems like a general volume problem with application of conversation of mass. please answer as soon as you can. thank you

4. Draining bathtub A bathtub of lenghth L and width W is lled to an intitial height H of water. A drain of crosssection A at the bottom of the tub is opened, and the water drains through it at speed 1: = m, where Mt) is the height of water in the bathtub at time t. Using conservation of mass, derive an expression for Mt)