Problem 12 In a memory hierarchy organization with two levels of caches, main memory, and disk assume that: . . . Cache Level Ll has access time Tcl= 5 ns and its hit ratio h1= 90%. Cache Level L2 access time Tc2-20 ns and its hit ratio h2-8000 Main memory access time Tm-80 and its hit ratio h3 : 60 % Disk access time Td- 1000 ns. Find average memory access time. Show details of your solution. (15 points)