Memory Paging I'm having trouble understanding this question (1996 exam, pg. 40, qs. 54-55):

Consider a virtual memory with M resident pages and a periodic page reference string

p[1], p[2], ..., p[n], p[1], p[2], ..., p[n], p[1], p[2], ..., p[n]

of N distinct requests.

Assume that the string of N requests was constructed randomly, and assume that initially none of the pages are resident.

Assume that N = 2M and FIFO is used. If the string p[1], p[2], ..., p[n] is repeated three times, then the number of page faults is

(a) N/2 (b) N (c) N + 3 (d) 2N (e) 3N