Cost analysis. The company in Problem $85$ produces the same camp stove at another plant. The total cost $C(x)($in dollars$)$ of producing $x$ camp stoves per week at plant $B$ is shown in the figure. Discuss the graph of the marginal cost function $C^{\text{'}}(x)$ and interpret the graph of $C^{\text{'}}(x)$ in terms of the efficiency of the production process at plant $B.$ Compare the production processes at the two plants.