Consider a system using preemptive Shortest Job First algorithm. The systems is running tasks P1, P2, P3, and P4, whose arrival times are 0, 3, 4, and 5 and whose CPU time bursts are 6, 2, 7, and 19, respectively. Assumption: The CPU time bursts are in measures of milliseconds (ms).       a. Draw a Gantt chart showing the execution schedule.           b. What is the average waiting time?           c. What is the turnaround time for process P3 under the preemptive Shortest Job First algorithm?

5-Consider a computer running a program that requires 400 s, with 80 s spent executing FP instructions, 40 s executed L/S instructions, and 40 s spent execut- ing branch instructions. • By how much is the total time reduced if the time for FP operations is reduced by 5%? • By how much is the time for INT operations reduced if the total time is reduced by 5%? • Can the total time can be reduced by 10% by reducing only the time for branch instructions?

Consider a system of three independent, periodic real-time tasks: T1= (4, 3), T2 = (12,7), and T3 = (8, 5). Construct the schedule for these tasks in the interval [0, 24) with q=1 on twoprocessors with PF. Note that there are many PFair algorithms, while PF is one of them. PF prioritize subtasks by deadlines, and break ties by inspecting future subtask deadlines. Also, if a currently-executing job ties with a newly- released job, then continue executing the currently-executing job; break any other ties by task ID (T1 = highest, T3 = lowest). a. Show all sub jobs’ releases and deadlines for (the first job of) each task. Note that q=1 so each sub job should have execution requirement of 1b. Show the PF schedule.c. Will this task set be schedulable with q=2? Please explain.

Q3: Suppose there is a processing unit composed by CPU and I/O component. For a specific task, CPU takes 5 second to finish the execution and I/O takes 2 second to process. The communication time between CPU and I/O can be elimiate under this circumstance. Execution Time 7 second 5second 2 second CPU time I/O time If CPU time decreases by 25% per year for 3 years and I/O time decreases by 20% per year 1) How many times faster is this program after 3 years? 2) What percentage of new time is I/O? and what percentage of new time is CPU?