1. Now suppose that the information given in the previous problem is listed in preference order, i.e., the book the student desires most is listed first. Use these preferences to create a weighted graph, and try to find a minimum weight matching.
2. In Figure 10.23 we have a puzzle with partial solution (1,∗,∗,∗,2,∗,∗,∗,∗). The rules are that we must place a 1, 2, and 3 in every row and every column. Follow a backtracking procedure to solve the puzzle. How many possible solutions are there?
