$2$a$.[$Points $5]$ Suppose a disk drive has $3000$ cylinders, numbered $0.\mathrm{.}2999.$ The drive is currently serving a request at cylinder $1800.$ It previously served a request at cylinder $1500.$ The queue of pending requests, in FIFO order, is: $1500,500,1200,2300,300.$ Starting from the current head position, what is the total distance $($in cylinders$)$ that the disk arm moves to satisfy all the pending requests for FCFS disk$-$scheduling algorithm?

$2$b$.[$Points $5]$ Suppose a disk drive has $3000$ cylinders, numbered $0.\mathrm{.}2999.$ The drive is currently serving a request at cylinder $1800.$ It previously served a request at cylinder $1500.$ The queue of pending requests, in FIFO order, is: $1500,500,1200,2300,300.$ Starting from the current head position, what is the total distance $($in cylinders$)$ that the disk arm moves to satisfy all the pending requests for SSTF disk$-$scheduling algorithm?

$2$c$.[$Points $5]$ Suppose that a disk drive rotates at $10,000$ RPM$.$ It has an average seek time of $6$ milliseconds. If its transfer rate is $40$ Mbps $,$ determine the average time it takes for a $1$ Mbyte request to be transferred from the time the disk starts the seek? $\backslash ((1\backslash$mathrm$\{$~K$\}=1024$ ; $1\backslash$mathrm$\{$M$\}=1024\backslash$mathrm$\{$~K$\})\backslash )$

$2$d$.[$Points $5]$ Consider a RAID level $6$ system with $4$ disks $($numbered $1-4)$ as shown in the below figure. Answer the following questions $($i$)$ Which of the disks need to be accessed to read data block B$1?($ii$)$ Which of the disks need to be accesses to write block B$1?$