Consider a paging system with the page table stored in memory. If a memory reference takes $200$ nanoseconds, how long does a paged memory reference take? If we add a Translation Lookaside Buffer (TLB) and $75$ percent of all page-table references are TLB hits, what will then be the effective memory reference time? Assume that finding a page-table entry in the TLB takes $20$ nanoseconds, if the entry is present.