Help me for those Operation System questions

1. FCFS(First-Come First-Served): Consider a system with tasks P1, P2, and P3 with time bursts of 20, 10, and 1 ms, respectively. Draw a Gantt chart representing the schedule if the tasks arrive in order: P1, P2, P3. What is the average waiting time?

2. Consider a system using preemptive SJF algorithm. The systems is running tasks P1, P2, P3, and P4, whose arrival times are 0, 1, 2, and 3 and whose CPU time bursts are 10, 1, 3, and 20, respectively. Draw a Gantt chart showing the execution schedule. What is the average execution time?

3.Now, assume the system in previous uses a preemptive (SJF) scheduler. Draw a Gantt chart showing the schedule. What is the average waiting time

4. Is it possible to achieve true parallelism with one-to-many model? One-to-one model? Many-to-many model?

5. What are the three requirements for synchronization?

6. Illustrate how race conditions may occur even on single processor systems.