an engine is pumping water from a large tank delivering it through a pipe of diameter 0.04m at a rate of 100 litres per second. Find the work done by the pump (mass of 1 litre is 1 kg)

at a loss with this question.

im assuming pump is horizontal so no PE (?)

then 100 litres= 0.1m^3

and volume is L(pi(0.02)^2=0.001256L (L = length of pipe)

so 0.001256L=.1m^3

L=79.62

so in 1 second 100 kg of water moves 79.62 so

KE=(0.5)(100)(79.62)^2=3.17x10^5 which is correct answer, but have i just stumbled across this by accident or is my reasoning ok?