There are some duplicated requests. If the file names are the same, they are the same file. The hard drive disk spins at $7200$rpm$.$ The data transfer rate of the main memory is $2000M\frac{B}{s},$ and the data transfer rate of the disk is $100M\frac{B}{s}.$ It takes $0\mathrm{.}1ms$ to traverse one track. For example, it takes $1ms$ to move from track $50$ to track $60.$ If the last visited track is $50$ and the direction of the arm is increasing.