Consider the famous dining philosopher's problem. Five philosophers are sitting around a table with five forks between them. Each philosopher must pick up both forks on her left and right before she can start eating. If each philosopher first picks the fork on her left, then all will deadlock while waiting for the other fork. The goal is to come up with an algorithm that lets all philosophers eat, without deadlock or starvation. a. What is deadlock? b. Write a solution to this problem using semaphores.