7. (10 points)Consider a DMA module that is transferring characters (as bytes), one at a time, to main memory from some I/O device connected directly to the DMA device. Suppose that I/O device transfers bit-by-bit at a rate of 4800 bits per second. Suppose the CPU can fetch 684000 instructions per second (with constant use of the system bus and main memory). How much will the processor be slowed down due to the DMA activity? 8. (10 points) A computer has a cache, main memory, and a disk used for virtual memory. If a referenced word is in the cache, 20ns are required to access it. If it is in main memory but not in the cache, 20ns are needed to load it into the cache (this includes the time to originally check the cache), then the reference is started again. If the word is not in main memory, 47 ns are required to fetch the word from disk, followed by 20 ns to copy it to the cache, then the reference is started again. The cache hit ratio is 0.8 and the main memory hit ratio is 0.8. What is the average time in ns required to access a referenced word on this system