Formulate an algebraic model for the problem. Use LINGO or the Excel Solver to solve this model, with your name and student number included in a comment line. Copy-and-paste the model and solution LINGO files. If you solve the models in Excel Solver, you will have to write them in standard form, i.e. all variables on the left-hand side, and a number of the right-hand side. If you use LINGO, you are not bound by this restriction.

2. Drivers in the London (England) Underground railway system work two four-hour shifts per day. In some cases, the two shifts are consecutive (effectively one eight- hour shift), but usually they are not. All Underground drivers earn a base rate of 21 per hour (i.e. 168 per day). Because of the inconvenience of breaking up the day, those who work non-consecutive shifts are paid a 15 per day bonus. The London Underground has the following daily requirements for drivers: Minimum Number Shift Time of Day of Drivers Needed 1 0500 to 0859 430 2 0900 to 1259 150 3 1300 to 1659 230 4 1700 to 2059 390 5 2100 to 0059 270 No-one will be asked to work on both shifts 1 and 5. Subject to meeting all its requirements for drivers, the London Underground wishes to minimize its daily labour cost (regular and bonus). Formulate the model so that the 21 (or 168) and the 15 are entered only once