Answer
$V=0.0291\frac{m^3}{s}$
Work Step by Step
Here we are working with potential energy. First we calculate the power we are going to have:
$W=(7hp*\frac{745.7W}{1hp})*0.82=4280.32W$
Knowing that: $W=mgh=\rho Vgh$:
$V=\frac{W}{\rho gh}=\frac{4280.32W}{1000\frac{kg}{m^3}*9.81\frac{m}{s^2}*15m}=0.0291\frac{m^3}{s}$
