II. In a computer system, the main memory has an access time of 1000ns. The cache access is 100ns. Suppose that 100 access to memory are found in cache and 25 are fetched from main memory. (7 points) a. Find the hit ratio. (2 points) b. Find the miss ratio (1 point) c. Find the mean access time. (3 points) d. What is the improvement in performance that resulted from using the cache in this system? (1 point) 9