Consider the following page reference string $1,2,3,4,2,1,5,6,2,1,2,3,7,6,3,2,1,2,3,6.$ Find out the number of page faults, hit ratio, and miss ratio if there are $4-$page frames, for the FIFO, Optimal, and LRU page replacement algorithms. And identify which algorithm generates high page faults.