You are building a system around a processor with in-order execution that runs at 1.1 GHz and has a CPI of 0.7 excluding memory accesses. The only instructions that read or write data from memory are loads (20% of all instructions) and stores (5% of all instructions). The memory system for this computer is composed of a split L1 cache that imposes no penalty on hits. Both the I-cache and D-cache are direct mapped and hold 32 KB each. The I-cache has a 2% miss rate and 32-byte blocks, and the D-cache is write-through with a 5% miss rate and 16-byte blocks. There is a write buffer on the D-cache that eliminates stalls for 95% of all writes. The 512 KB write-back, unified L2 cache has 64-byte blocks and an access time of 15 ns. It is connected to the L1 cache by a 128-bit data bus that runs at 266 MHz and can transfer one 128-bit word per bus cycle. Of all memory references sent to the L2 cache in this system, 80% are satisfied without going to main memory. Also, 50% of all blocks replaced are dirty. The 128-bit-wide main memory has an access latency of 60 ns, after which any number of bus words may be transferred at the rate of one per cycle on the 128-bit-wide 133 MHz main memory bus. (a) What is the average memory access time for instruction accesses