Question Consider the cost function $C(x)C(x)=1,000+x+\frac{1}{4}{x}^2,$ where $x$ is the number of product units. If the marginal cost at $x=400$ units is $-$$$100,$ what is the value of $?$ Question Consider the cost function $C(x)C(x)=1,000+x+\frac{1}{4}{x}^2,$ where $x$ is the number of product units. If the marginal cost at $x=400$ units is $-$$$100,$ what is the value of $?$ Question Consider the cost function $C(x)$