Using the information below,

CPU W = 4 ms (the average time to execute 1,000 instructions)

Drive A = 45 ms (average data access speed)
Drive B = 3 ms (average data access speed)
Drive C = 17 ms (average data access speed)
Drive D = 10 ms (average data access speed)

Calculate I/O access speed using this CPU and each of the four disk drives as they evaluate the following track requests in this order: 0, 31, 20, 15, 20, 31, 15. Then, in each case, calculate the access speeds after the track requests are reordered and rank the four disk drives before and after reordering. (See section: Role of Device Management in chapter for this and next question)