2400 revolution in 60 sec
1 revolution in 25 ms
Average rotational latency = 0.5*revolution time =12.5 ms
p=12.5 ms
1 revolution time = time to cover 1 track
25 ms = 1 track time
1 track = 62500 bits
62500 bits in 25 ms
2500 bits in 1 ms
2500000 bits in 1 sec
or 25*$10^{5}$bits per second =Q