Given a set ={1,2,…,} of tasks, where requires pp units of processing time to finish once it has started. There is only one computer to run these tasks one at a time. Let cc be the completion time of task The goal is to minimize the average completion time 1 ∑ c =1 . For example, two tasks 1 and 2 have processing times p1= 3 and p2 = 5 respectively; running 1first results in the average completion time (3 + 8)/2 = 5.5, while running 2 first results in the average completion time (5 + 8)/2 = 6.5. (1) Describe 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.