A computer has a two-level virtual memory system. The main memory M1 and the secondary memory M2 have average access times of 10-6 and 10-3s, respectively. It is found by measurement that the average access time for the memory hierarchy is 10-4s, which is considered unacceptably high. Describe two ways in which this memory access time could be reduced from 10-4 to 10-5 and discuss the hardware and software costs involved.