Can anyone help me? I'll give 20 points

A weir is used to measure water flow in a channel. For a rectangular broad crested weir, the flow Q in cubic feet per second is related to the weir length L in feet and height H of the water by Q = 1.6LH3/2. Find the water height for a weir that is 3 feet long and has a flow of 38.4 cubic feet per second.