Q5-a

The access times of the main memory and the Cache memory, in a computer system, are $500$ n sec and $50$ nsec, respectively. It is estimated that $80\%$ of the main memory request are for read the rest for write. The hit ratio for the read access only is $0.9$ and a write-through policy (where both main and cache memories are updated simultaneously) is used. Determine the average time of the main memory (in ns).