hey can you provide me answer to this question.Please Answer it step by step

Consider a weighted form of the activity selection problem of CLRS3 section 16.1 in which each of the n activities is weighted by its importance (the weight is unrelated to the starting and finishing times and to the duration). We want to choose a subset of non-conflicting activities with the highest total weight. Prove that the heuristic of choosing the earliest finishing time does not always result in an optimal schedule. Give an 0(n^2) algorithm to compute an optimal schedule