please help !

explain it step-by-step and please use standard style pont!

Problem 4 (Problem 2.15 in Wilkes) A tank of cross-sectional area A initially (t = 0) contains two layers, each of depth H: oil (density po) and water (density pw). A sharp edged orifice of cross-sectional area a and coefficient of contraction 0.62 in the base of the tank is opened. Derive an expression for the time t taken for the water to drain from the tank, in terms of H, g, A, a, po, and pw. Neglect friction and assume that A >> a. You may find the example on pages 70-71 of the Wilkes textbook helpful. (25 pts) Initial level Oil 2H H Water h (1) 2=0 Water exit