Review the system with one CPU and four drives 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.