Question $9.$ Demand paging is used for the following reasons. Pick the most apprpriate statements? Question $10.$ Given the refrence string $1,2,3,4,5,2,1,3,2,1,5,4,1.$ How many page faults occur using FIFO algorithm with $3$ frames? Question $11.$ Disk scheduling needed for the following reasons. Question $12.$ There is no optimal solution to access disk. Question $13.$ For a $1$ TB disk $1$ MB block size. How many blocks are there $?$