RAIDs. For this question, we'll examine how long $($How many total writes$)$ it takes to perform a small workload consisting of $12$ writes to random locations within a RAID. Assume that these random writes are spread "evenly" across the disks of the RAID. Show your work. $(12$ points$)$

a$.$ Assume we have a $4-$disk RAID$-0($striping$).$ How long does it take to complete the $12$ writes?

b$.$ How long on a $4-$disk RAID$-1($mirroring$)?$

c$.$ How long on a $4-$disk RAID$-4($block parity$)?$

d$.$ How long on a $4-$disk RAID$-6($Double rotated parity$)?$