Question 1. A post-office is planning on selecting routes for mail delivery. It will choose routes to deliver mails to six areas: A, B, C, D, E and F. There are 10 potential routes to choose from, which are given in the following table with their lengths (in miles). Use an integer program model to help the post-office choose the routes to serve all six areas with a minimum total traveling distance (specify your decision variables, objective function and constraints). Solve your model with Excel Solver. (Check value - optimal obj. value is 24) Route # Route Length 1 A-B 8 2 B-C-D 11 3 A-E-F 13 4 C-F 8 5 B-E 8 6 B-C-F 7 A-C-F 9 8 C-E-F 12 9 A-D 9 10 D-E 9 10 To share resource, the post office has the following preferences: (1) If route 2 is selected, route 4 should be selected, but route 7 should not be selected; (2) At most 3 routes should be selected. Incorporate this into the integer program and solve it again (on a new worksheet). Check value - optimal obj is 25