Consider a demand-paging system with a paging disk that has an average access/transfer time of 50 ms. Addresses are translated through a page table in main memory, with an access time of 500 ns per memory access. Thus, each memory reference through the page table takes two accesses. To improve this time, we have added a TLB that reduces access time to one memory reference if the page-table entry is in the TLB. Assume that 80% of the accesses are in the TLB and that, of those remaining, 10% cause page faults. We assume that the TLB access time is 20 ns. What is the effective access time? Show both the formula and the final result.