= Solution
The preemptive policy improves B's <scheduling turnaround time> from 17 to 10 ms and the mean from 16.5 to 14 ms. A finishes later, at 18 rather than 16 ms, and the total completion time rises from 17 to 18 ms. Thus \b[preemption improves mean turnaround here; nonpreemption gives the shorter makespan here].
The result illustrates different scheduling objectives, not a universal winner. These calculations assume negligible <context switch> overhead; charging for the additional switches could change the comparison. Both policies perform the same 15 ms of useful <CPU> work.
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