Question 1 21 marks totall Part A 115 marks] There are four processes; A, B, C and D that will be running on a system with a single processor. The processes are each characterized as only requiring CPU time (i.e. the processes will not generate/require any I/O requests). The operating system uses the five state model. Table 1 below shows the arrival time into the Ready state for each process and their required CPU time. Assume that the CPU can start at time 0. For a), b), c), d) ignore the time needed for a context switch. Table 1: Process arrival time and required CPU time. Process Arrival Time (us) CPU time (us 20 40 50 70 40 10 40 a) [3 marks] Calculate the mean (average) turnaround time if the operating system uses a non-preemptive First-In-First Out scheduler. 13 marks] Calculate the mean (average) turnaround time if the operating system uses pre-emptive First-In-First Out scheduling. b) c) [3 marks] Calculate the mean (average) turnaround time if the operating system uses pre-emptive Shortest Job First scheduling. 13 marks] Calculate the mean (average) turnaround time if the operating system uses a Round-Robin scheduler with a 10 us quantum. d) [3 marks] If the context switch time is 5 s, calculate the mean (average) turnaround time for both an operating system that uses a pre-emptive Shortest Job First scheduler and an operating system that uses a Round-Robin scheduler with a 10 Hs quantum. e)