$[-/3$ Points$]$

Suppose that the cost function for a commodity is

$C(x)=30x^2$ dollars

$($a$)$ Find the marginal cost at $x=4$ units.

$\frac{?}{\text{b}\text{a}\text{r}}(MC)(4)=$

$$

Tell what this predicts about the cost of producing $1$ additional unit.

The cost to produce the $5$th unit is predicted to be $ $.$

$($b$)$ Calculate $C(5)-C(4)$ to find the actual cost of producing $1$ additional unit.

$ $$

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