A computer system consists of three level memory organizations. The capacity of direct mapped L1 cache memory is of 4096 bytes where as the 8-way set associative L2 cache memory is of 512 Kbytes. The access time of L1 and L2 cache is 10 nsec and 20 nsec respectively. The Main memory access time is 200 nsec. The hit rate of L1 cache is 75%. Calculate the hit ratio for L2 cache memory, if the average memory access time is 50 nsec?