The cost of producing $x$ ounces of gold from a new gold mine is $C=f(x)$ dollars.
(a) What is the meaning of the derivative $f^{\prime}(x)$ ? What are its units?
(b) What does the statement $f^{\prime}(800)=17$ mean?
(c) Do you think the values of $f^{\prime}(x)$ will increase or decrease in the short term? What about the long term? Explain.