Problem 9.13. Let A H be a set of tasks that we must complete. The following DAG de scribes which tasks must be done before others, where there is an arrow from a to b iff a must be done before b (a) Write the longest chain. (b) Write the longest antichain (c) If we allow parallel scheduling, and each task takes 1 minute to complete, what is the minimum amount of time needed to complete all tasks