4. A system has three processes (PI, P2, and P3) and three resources (R1, R2, and R3). There are two re R1, R2, and R3). There are two resources of Rl and R3. There is one resource of R2. Pl holds an RI and an R3 and is requesting an R2. P2 holds an RI and an R2 and is requesting an R3. P3 hold an R3 and is requesting an R2. Draw the resource allocation graph for this situation. Does a deadlock exist? Why or why not (explain) (10 points)