A program consists of n threads. Each thread works in phases. Each thread begins in phase 1

) A program consists of n threads. Each thread works in phases. Each thread begins in phase 1. It is required that all threads complete phase 1 before they can begin phase 2. Likewise, each thread must complete phase 2 before any thread can begin phase 3, and so on. So, the code for each thread has the following structure. for (i = 1; ;i++) { Execute phase i WaitForBarrier(i, threadid); } The function WaitForBarrier ensures that if a thread finishes phase i too quickly then it is blocked. When all threads finish phase i, they are resumed so that they can continue executing phase i+1. Write the function WaitForBarrier(int, int) using semaphores. Explain the correctness of your solution.