What is meant by power?

A water pump lifts water from a level $10 \mathrm{m}$ below the ground. The water is pumped at the rate of$30 \mathrm{kg}/\min$ with negligible velocity. Calculate the minimum power the pump should have to do this work.

Pratyush can run at a speed of $8 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.$ against the frictional force of $10 \mathrm{N}$. His friend Adarsh can move at a speed of $3 \raisebox{1ex}{$\mathrm{m}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.$ against the frictional force of $25 \mathrm{N}$. Who is more powerful and why?