2. Consider the program below with two threads running concurrently. Add the necessary synchronizations so that this programs satisfies the precedence constraint C1 C2, i.e. thread B must not start executing C2 before thread A has finished executing C1. To solve the exercise, replace the ? with the correct code. In the left most box, Choose the initial value of the semaphore. In the other two boxes call S.wait() and S.signal() to solve the problem. Thread A Thread B Initial conditions Semaphore S =? 2 C1; 1? 2 C2; 3 ? 3 ?