3. a. Explain with the help of a diagram how the L'O devices coordinate with the processor, main memory, and cache. (2 Marks) b. Given the following specifications, calculate the average time for reading a 4 KB sector (of Disk Speed-10000 RPM, average seek time 5 m sec, data transfer rate- 100MB/sec, and data) on disk into main memory: controller overhead 0.1 m sec. (2Marks) c. Describe the RAID3 and RAID4 disk systems clearly bringing out their differences particularly with respect to writing new data blocks (2 Marks)