A hierarchical memory system that uses cache memory has cache access time of 50 nano seconds, main memory access time of 300 nano seconds, 75% of memory requests are for read, hit ratio of 0.8 for read access and the write-through scheme is used. What will be the average access time of the system both for read and write requests ?

• A. 157.5 n.sec
• B. 110 n.sec
• C. 75 n.sec
• D. 82.5 n.sec