USE LINGO or ill down vote

5. (20 marks) A helicopter at location which is at an offshore supply base in St. John's, needs to visit all four offshore platforms on one trip. These platforms are denoted as locations 1, 2, 3, and 4. The distance in km that it would take a helicopter to travel from one location to another is given in the following table. Because these are distances in the air, the table is symmetric. From 0 1 2 3 4 0 1 0 219 219 0 286 70 150 94 418 261 2 3 4 286 150 418 70 94 261 0 164 210 164 0 349 210 349 0 The objective is to minimize the total distance travelled. (a) Define the variables for this model. Write them as part (a) in Word or pdf, or embed them at the top of the file in part (b). (b) Omitting the sub-tour constraints, write the model using LINGO or the Excel Solver, and solve this (partial) model. Show that this solution is not a tour, and state the two sub-tours. (c) Give a constraint that would, if added to the formulation of (b), prevent this specific situation from arising. Re-solve the computer model, and state whether or not this new solution is a tour. (d) If necessary, repeat (c) until a tour is obtained