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Active Calculus 1st Ed

Activity 1.5.3.
A company manufactures rope, and the total cost of producing \(r\) feet of rope is \(C(r)\) dollars.
(a)
What does it mean to say that \(C(2000) = 800\text{?}\)
(b)
What are the units of \(C'(r)\text{?}\)
(c)
Suppose that \(C(2000) = 800\) and \(C'(2000) = 0.35\text{.}\) Estimate \(C(2100)\text{,}\) and justify your estimate by writing at least one sentence that explains your thinking.
(d)
Do you think \(C'(2000)\) is less than, equal to, or greater than \(C'(3000)\text{?}\) Why?
(e)
Suppose someone claims that \(C'(5000) = -0.1\text{.}\) What would the practical meaning of this derivative value tell you about the approximate cost of the next foot of rope? Is this possible? Why or why not?