When a running process experiences a page fault, the frame to hold the missing page can only come from those frames allocated to that process, not from frames used by any other process. The memory system chooses which frame to use using a simple first-in first-out technique. That is, the first time it must choose a frame to use to hold a page being loaded to resolve a page fault, it chooses the first frame it loaded originally. The second page fault then uses the now oldest frame (the second one that had been loaded originally), and so on: the first frame (originally) loaded becomes the first frame out (i.e. to be reused). Each page fault causes only the one missing page to be loaded. Now suppose a program is executing a straight, linear sequence of instructions that is 100 Kbytes long. This process is allocated 20 frames, each 4 Kbytes big, when put into memory.

a. How many page faults will there be to completely execute this sequence of instructions?

b. Finally, suppose the 100 Kbyte block of instructions is a loop that repeats infinitely. How many page faults are there on the second iteration of the loop?