CPU Scheduling

Which one of the following CPU scheduling algorithms cannot be preemptive?

Processes $P1$, $P2$, $P3$, $P4$ arrive in that order at times 0, 1, 2, and 8 milliseconds respectively, and have execution times of 10, 13, 6, and 9 milliseconds respectively. Shortest Remaining Time First (SRTF) algorithm is used as the CPU scheduling policy. Ignore context switching times. Which ONE of the following correctly gives the average turnaround time of the four processes in milliseconds?

Consider a single processor system with four processes A, B, C, and D, represented as given below, where for each process the first value is its arrival time, and the second value is its CPU burst time. A (0, 10), B (2, 6), C (4, 3), and D (6, 7). Which one of the following options gives the average waiting times when preemptive Shortest Remaining Time First (SRTF) and Non-Preemptive Shortest Job First (NP-SJF) CPU scheduling algorithms are applied to the processes?

Which of the following statement(s) is/are correct in the context of CPU scheduling?

Consider the set of processes with arrival time (in milliseconds), CPU burst time (in milliseconds), and priority (0 is the highest priority) shown below. None of the processes have I/O burst time. $$\begin{array}{|c|c|c|c|} \hline \text{Process} & \text{Arrival Time} & \text{Burst Time} & \text{Priority} \\ \hline P_1 & 0 & 11 & 2 \\ P_2 & 5 & 28 & 0 \\ P_3 & 12 & 2 & 3 \\ P_4 & 2 & 10 & 1 \\ P_5 & 9 & 16 & 4 \\ \hline \end{array}$$ The average waiting time (in milliseconds) of all the processes using preemptive priority scheduling algorithm is ________.

Consider the following processes, with the arrival time and the length of the CPU burst given in milliseconds. The scheduling algorithm used is preemptive shortest remaining-time first. $$\begin{array}{|c|c|c|} \hline \text{Process} & \text{Arrival Time} & \text{Burst Time} \\ \hline P_1 & 0 & 10 \\ P_2 & 3 & 6 \\ P_3 & 7 & 1 \\ P_4 & 8 & 3 \\ \hline \end{array}$$ The average turn around time of these processes is ________ milliseconds.

Three processes A, B and C each execute a loop of 100 iterations. In each iteration of the loop, a process performs a single computation that requires $t_c$ CPU milliseconds and then initiates a single I/O operation that lasts for $t_{io}$ milliseconds. It is assumed that the computer where the processes execute has sufficient number of I/O devices and the OS of the computer assigns different I/O devices to each process. Also, the scheduling overhead of the OS is negligible. The processes have the following characteristics: $$\begin{array}{ccc} \textbf{Process id} & t_c & t_{io} \\ A & 100 \text{ ms} & 500 \text{ ms} \\ B & 350 \text{ ms} & 500 \text{ ms} \\ C & 200 \text{ ms} & 500 \text{ ms} \end{array}$$ The processes A, B, and C are started at times 0, 5 and 10 milliseconds respectively, in a pure time sharing system (round robin scheduling) that uses a time slice of 50 milliseconds. The time in milliseconds at which process C would complete its first I/O operation is _____.