A Web-based brokerage company runs a site consisting of a web server, an application server and a database server. The database server has two processors and three disks. The application server converts business functions from the web server into transactions that are submitted to the database. On average, each user visit to the web site generates 6 consecutive business functions and each business function generates 1.5 database transations. An average transaction generates 2 accesses to disk A, 3 accesses to disk B, 2 accesses to disk C and a total of 6 CPU bursts which are evenly distributed across the two processors. Average service times per access at the three disks are 40, 30 and 25 milliseconds respectively, while average service times at the database processors are 30 milliseconds per burst. The average service demand of each business function is 150 milliseconds at the web server and 130 milliseconds at the application server. On average, a user thinks for 20 seconds between each business function. For all parts you should state which operational laws you are using and explain your reasoning. a.) Which is the bottleneck device in the database? 3 marks b.) What is the minimum average residence time per transaction, regardless of the number of users using the system? 3 marks c.) What is the maximum possible utilisation of disk C and when would this be achieved? 3 marks d.) How many users would be using the system if the average response time per business function is 8 seconds and the throughput at disk C is 0.002 (accesses/millisecond)? 3 marks e.) What revised service time per access at disk A would you recommend to achieve a system response time per business function of 5 seconds when there are 100 users on the system? Which other devices, if any, would need to be speeded up to achieve this target?