Let $${a_n}$$ be the number of $$n$$-bit strings that do NOT contain two consecutive $$1s.$$ Which one of the following is the recurrence relation for $${a_n}$$?

Consider a computer system with ten physical page frames. The system is provided with an access sequence $$\left( {{a_1},{a_2},....,{a_{20}},{a_1},{a_2},...,{a_{20}}} \right),$$ where each $${{a_i}}$$ is a distinct virtual page number. The difference in the number of page faults between the last-in-first-out page replacement policy and the optimal page replacement policy is _____________

Consider a computer system with $$40$$-bit virtual addressing and page size of sixteen kilobytes. If the computer system has a one-level page table per process and each page table entry requires $$48$$ bits, then the size of the per-process page table ____________ is megabytes.

Consider an arbitrary set of $$CPU$$-bound processes with unequal $$CPU$$ burst lengths submitted at the same time to a computer system. Which one of the following process scheduling algorithms would minimize the average waiting time in the ready queue?