Formulate but do not solve an algebraic model for the following situation. City bus drivers 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 drivers earn a base rate of $26.25 per hour (i.e. $210 per day). Because of the inconvenience of breaking up the day, those who work non-consecutive shifts are paid a $18 per day bonus. The city bus service has the following daily requirements for drivers:

shift	time of day	minimum number of drivers needed
1	0500 to 0859	150
2	0900 to 1259	80
3	1300 to 1659	90
4	1700 to 2059	160
5	2100 to 0059	70

Nobody will be working on both shifts 1 and 5. Subject to meeting all its requirements for drivers. the city bus service wants to minimize its daily labour cost (regular and bonus)