CPU Scheduling

For the processes listed in the following table, which of the following scheduling schemes will give the lowest average turnaround time? $$\begin{array}{|c|c|c|} \hline \text{Process} & \text{Arrival Time} & \text{Processing Time} \\ \hline A & 0 & 3 \\ B & 1 & 6 \\ C & 4 & 4 \\ D & 6 & 2 \\ \hline \end{array}$$

An operating system uses shortest remaining time first scheduling algorithm for pre-emptive scheduling of processes. Consider the following set of processes with their arrival times and CPU burst times (in milliseconds): $$\begin{array}{c|c|c} \textbf{Process} & \textbf{Arrival Time} & \textbf{Burst Time} \\ \hline P1 & 0 & 12 \\ P2 & 2 & 4 \\ P3 & 3 & 6 \\ P4 & 8 & 5 \end{array}$$ The average waiting time (in milliseconds) of the processes is _____.