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