Answer:
6 buses and 10 vans
Step-by-step explanation:
It is convenient to solve this graphically. The problem setup is ...
minimize 975b + 350v subject to ...
40b +8v ≥ 320 . . . . . regular seats required
1b +3v ≥ 36 . . . . . . . .handicapped seats required
where b and v are the numbers of buses and vans, respectively.
The constraint lines intersect at (b, v) = (6, 10). 6 buses and 10 vans will provide the required number of seats at minimum cost.
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At any other point in the feasible region, the cost line (green) will be farther from the origin, hence the cost will be greater.
In the attached, x represents buses; y represents vans.