1. A memory subsystem has the following specifications. (i) Cache takes 80 nsec to access the index field of each set. (ii) Cache takes 10 nsec to access the tag field of each set. (iii) Main memory access time of 500 nsec. (iv) 80% memory request are for reads. (v) Hit ratio 0.9 for read access and 0.8 for write access. Compute the following. (a) Average access time for read. (b) Average access time for write and overall (both read and write) for write through scheme. (c) Average access time for write and overall (both read and write) for write back scheme. (d) Average hit ratio