The cost, in dollars, of producing $x$ gallons of wood stain is given by the following function:
$C(x)=3200+0.1x-0.001x^2+0.0004x^3$
**What is the instantaneous rate of change of the cost when $100$ gallons are produced?**
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**In what units is this rate of change measured?**
[[☃ radio 2]]