Consider a RAID-4 disk configuration involving five disks A, B, C, D and E where disk E stores the parity. Examine the following six scenarios involving read and write operations in the presence of disk failures in this configuration: All disks are up. There is a write operation on block 10 of disk C. Disk B is down and all other disks are up. There is a read operation on block 20 of disk C. Disk C is down and all other disks are up. There is a read operation on block 30 of disk C. Disk D is down and all other disks are up. There is a write operation on block 40 of disk C. Disk E is down and all other disks are up. There is a read operation on block 50 of disk C. Disk E is down and all other disks are up. There is a write operation on block 60 of disk C. In each of the above scenarios determine how many disk accesses happen in order to process the I/O operation. Assume that the goal is to allow as many of the I/O operations as possible, in the presence of disk failures. When counting disk accesses do not count accesses to disks that are down.