calculus 2 work problem

Question

A chain 68 meters long whose mass is 20 kilograms is hanging over the edge of a tall building and does not touch the ground. How much work is required to lift the top 3 meters of the chain to the top of the building? Use that the acceleration due to gravity is 9.8 meters per second squared.

Answer 1

Work W = mgl/2 - mg(mg(l - 3)/2 = mg3/2 = 20kg·9.8m/s²·3m/2 = 294 J