Time taken for one full rotation = 60/6000 sec
= 1/100 sec = 0.01 sec = 10 msec
Average rotational delay = ½ x Time taken for one full rotation
= ½ x 10 msec = 5 msec
Transfer time = (512bytes / 40 kb) sec
= 0.0125 sec = 12.5 msec
Average access time = Avg. seek time + Avg. rotational delay + Transfer time + Controlled overhead + Queing delay
= 5 msec + 5 msec + 12.5 msec + 0.1 msec + 0
= 22.6 msec