4. (3.4) Let d be the maximum degree of concurrency in a task-dependency graph with t tasks and a critical-path length l. Prove that [t/l] d t l + 1. Note: [t/l] is meant to be the ceiling of t/l. Also note the equation contains both letter l and integer 1. This is trying set a relationship between the critical path length of a graph and maximum parallelism. For example, if the maximum parallelism is t (=number of tasks), then critical( path cannot be greater than 1. Likewise, if the maximum parallelism is 1, then the critical path must be at least t. You can use proof by contradiction.