Q4: Consider the following page reference string: 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3, 6. How many page faults would occur for the following replacement algorithms, assuming one, two, three, four, five, six, and seven frames? Remember that all frames are initially empty, so your first unique pages will cost one fault each. LRU replacement FIFO replacement I Optimal replacement Q5: Consider the following page reference string: 7, 2, 3, 1, 2, 5, 3, 4, 6, 7, 7, 1, 0, 5, 4, 6, 2, 3, 0, 1. Assuming demand paging with four frames, how many page faults would occur for the following replacement algorithms? LRU replacement . FIFO replacement Optimal replacement Q6: Explain what thrashing is. What is the negative effect that thrashing has? How do you avoid thrashing?