Present the system of linear equations that could be solved in order to obtain the PageRank (i) for each webpage i represented by a node in the graph below. Let denote the probability of teleportation.

1<-> 2

3 <-> 4

Consider the set of frequent 2-itemsets L2 = {{1, 2}, {1, 5}, {2, 3}, {2, 4}}. Compute the set of candidates C3 that would be generated by the Apriori algorithm by joining every possible pair of joinable itemsets from L2.