Physics problem on power involving escalators

[brnnpink4]

Homework Statement

An escalator at a mall lifts passengers 6m. The escalator has to be able to lift 50-75kg people at one time up the lift. The time to make it to the top is 40s. What must the power rating of the escalator be?

Homework Equations

w=fd

p=w/t

The Attempt at a Solution

w=6f

 

[Simon Bridge]

Please show your reasoning and your working.

When people get lifted up by the escalator, some energy changes: what kind?
This energy has to be supplied to the lift - power is the rate of change of energy.