4) A computer has a cache, main memory, and a disk used for virtual memory. In this system, the cache access time (TC) is 12 ns, the main memory access time (TM) is 45 ns, and the disk access time (TD) is 10 ms. The cache hit ratio (HC) is 0.92; if the referenced word is not in the cache, then the OS looks for it in main memory and has a hit ratio (HM) of 0.68. What is the average time (in ns) required to access a referenced word on this system? First, write the equation for EAT using the variables defined. Then, calculate EAT for this situation