In Exercises 53 and $54,$ the average cost per unit at production level $x$ is defined as $C_{\mathrm{avg}}(x)=C(x) / x,$ where $C(x)$ is the cost function Average cost is a measure of the efficiency of the production process.
The cost in dollars of producing alarm clocks is $C(x)=50 x^{3}-$ $750 x^{2}+3740 x+3750$ where $x$ is in units of $1000 .$
(a) Calculate the average cost at $x=4,6,8,$ and 10 .
(b) Use the graphical interpretation of average cost to find the production level $x_{0}$ at which average cost is lowest. What is the relation between average cost and marginal cost at $x_{0}($ see Figure 16$) ?$