The access time of cache memory is 100 ns and that of the main memory is 1 μsec. 80% of the memory requests are for reading and others are for write. The hit ratio for reading only accesses is 0.9. A write of the procedure is used. The average access time of the system for both read and write requests is

• A. 200 ns
• B. 360 ns
• C. 720 ns
• D. 1100 ns