2. (20pts) Consider the following variation of Activity Selection problem: Input: A set of n task a1, a2,.., an each expressed as ai-(ri di) where r is the release time, and di the time duration. All the tasks are executed by a single CPU without a time overlap after the time ri taking duration time di Output: Minimum finish time of the last executed task The difference from the original problem is ai- (release time, duration) changed from (start time, finish time): Each task a, is released at the time r, after which the CPU can execute it anytime taking duration di. So the CPU can finish all the tasks anyway. Now you don't maximize the number of executed tasks, but find a schedule with the earliest time to finish all. Design a greedy algorithm running in 0(n2) time to compute the problem. Write all of: o your basic method in 3-10 lines, o complete pseudo code, o proof of the algorithm correctness, and o that of the running time