Now these are all essentialy the same so I will do the first one and leave

the rest to you.

First sketch the feasible region defined by the constraints (see attachment).

The objective function takes its maximum and minimum at one of the

corners or vetices of the feasible region, so we evaluate it at each

at the maximum value it takes is the maximum on the feasible region,

and similarly the minimum value at a vertex in the minimum on the feasible

region.

The vertices are (0,45), (30,45), (60,20), (60,0), (0,0), and the objective

takes values : 315, 615, 740, 600, 0.

So the maximum value of the objective is 740, which is achieved at (60,20),

and the minimum is 0, which is achived at (0,0).

RonL