A pump propels water from a well which has a depth of $20\,m$ so that will be poured to a canal with a speed of $8\,\frac{m}{s}$. The volume which is to be pumped is $0.5$ Liters per second. Find the minimum power of the motor.

The alternatives given in my book are as follows:

$\begin{array}{ll}

1.&32\,W\\

2.&100\,W\\

3.&76\,W\\

4.&80\,W\\

5.&50\,W\\

\end{array}$

I'm confused about how to find the least power. What I thought to solve this problem was should I use the density of water so as to find the mass and from then calculate the power?. Can somebody help me with this question?.