5. a. C. Answer the following questions with short descriptions. What is the role of i-bit (invalid bit) in the Demand-Paging model? [ Marks 3] b. What is Belady's Anomaly? Marks 3] For the following reference string [7,0,1,2,0,3,0,4,2,3,0,3, 2] with Page frame=3, calculate the Hit-ratio for Least Recently Used (LRU) and Optimal Page Replacement (OPR) schemes. [ Marks 5+5] d. For the above problem i.e. Q5(c), if the average access time for hard-drive and memory are 150ms and 3ms respectively, then calculate overall time consumption while executing the given reference string [ Marks 4 ]