7. Periodic preventive maintenance is carried out on aircraft engines, where an important component must be replaced. The numbers of aircraft scheduled for such maintenance over the next six months are estimated at 200, 180,300,198,230, and 290, respectively. All maintenance work is done during the first day of the month, where a used component may be replaced with a new or an overhauled component. The overhauling of used components may be done in a local repair facility, where they will be ready for use at the beginning of next month, or they may be sent to a central repair shop, where a delay of TABLE 5.14 Unit Costs for Problem 4 Task type 1 2 3 4 5 1 10 2 3 15 9 Machine category 2 5 10 15 2 4 3 15 5 14 7 15 4 20 15 13 8 206 Chapter 5 Transportation Model and Its Variants TABLE 5.15 Bids per Acre for Problem 8 Location 1 2 3 1 $520 $210 $570

. d 2 $510 $495 Bid er 3 $650 $240 4 $180 $430 $710 3 months (including the month in which maintenance occurs) is expected. The repair cost in the local shop is $120 per component. At the central facility, the cost is only $35 per component. An overhauled component used in a later month will incur an additional storage cost of $1.50 per unit per month. New components may be purchased at $200 each in month 1, with a 5% price increase every 2 months. Formulate the problem as a transportation model, and determine the optimal schedule for satisfying the demand for the component over the next six months.