almost same like problem 6.4 on book
A.
best case: blocks are mapped sequential and on same cylinder. just seek data once.
T_avg_seek = 4ms
T_avg_rotation = 2ms
file size 2MB, block size 512B, block count 2MB/512B = 4000
Block Per Track = 1000, so we need rotate 4 loop to read all data
T_transfer = T_rotation = T_max_rotation * 4 = 16ms
so
T_access = 22ms
B.
worse case: blocks are random.
T_access = 4000 * (T_avg_seek + T_avg_rotation) = 24s