Q23

A cache memory that has a hit rate of $0.8$ has an access latency $10 \; \text{ns}$ and miss penalty $100 \; \text{ns}.$ An optimization is done on the cache to reduce the miss rate. However, the optimization results in an increase of cache access latency to $15 \; \text{ns},$ whereas the miss penalty is not affected. The minimum hit rate (rounded off to two decimal places) needed after the optimization such that it should not increase the average memory access time is _______________.