Recall and use the equation for the change in pressure beneath the surface of a liquid change in pressure = density × gravitational field strength × change in height, Δp = ρgΔh

Define power as work done per unit time and also as energy transferred per unit time; recall and use the equations (a) power = work done / time taken, P = W/t (b) power = energy transferred / time taken, P = ΔE/t