4] 25 points Consider a paging system with the page table stored in memory. a. If a memory reference takes 50 nanoseconds, how long does a paged memory reference take? b. If we add TLBs, and 75 percent of all page-table references are found in the TLBs, what is the effective memory reference time? (Assume that finding a page-table entry in the TLBs takes 2 nanoseconds, if the entry is present.)