Question

Hey for CalculusII when we're dealing with applications of integrals(Physics Problems) when doing work problems like a heavy rope of 50ft long weighs 0.51ib/ft and hangs over the edge of a building 120ft high, how do we construct our axis? i know there's two possible ways like we can start 0 at the top or zero at the bottom but i don't know what difference that will cause when computing the upper and lower bounds of the integral