Given a set ={1,2, ...,} of tasks, where requires units of processing time to finish once it has started. There is only one computer to run these tasks one at a time. The time before a task starts is called its waiting time . The goal is come up with a schedule to minimize the overall waiting time . (1) Give an example to show the greedy choice property and the optimal substructure in this problem, (2) Design a greedy algorithm to solve this problem,(3) Analyze the complexity of your algorithm.

2 1=1