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## Homework Statement

Suppose C(r) is the total cost of paying off a car loan borrowed at an annual interest rate of r%. What are the units of C '(r)? What are the units of C'(r)? What is its sign?

## Homework Equations

C'(r)=dC/dr

## The Attempt at a Solution

So, I figured:

C'(r) = dC/dr

Which is dollars over interest rate(?)...which seems kinda awkward to me. I'm wondering if theres a better solution for what the units of C'(r) would be. (dollars per percent interest?)

And I'm not sure what is meant by "What is it's sign"?