4a. In this case, we have 3 variables: the amount of plywood for surfaces, wood planks, and paint. Let's write some inequalities that will represent the constraints.
4b.
[tex]\begin{gathered} a\leq60ft^2 \\ b\leq36ft \\ 1qtWhere a := plywood [ft^2] ; b:=wood planks [ft] ; c = paint [qt].4c. In order to get the inequalities of the cost one must apply the instructions of the sentence. For example, since every plywood costs $0.70 per square foot, one should write it as A = 0.7 x a (where A is the cost of the plywood amount). Therefore, we write the following:
[tex]X=(0.7\cdot a)+(0.1\cdot b)+(8\cdot c)\begin{cases}X=\cos t \\ a=\text{plywood} \\ b=\text{planks} \\ c=\text{paint}\end{cases}[/tex]There is also the constraint of the cost, "Han's budget is $65", then the cost should be less than 65. One should write the following expression:
[tex]65\ge(0.7\cdot a)+(0.1\cdot b)+(8\cdot c)[/tex]