# Calculus: Derivatives: General Problems – #28142

Question: The cost of manufacturing x units of a product is $$C\left( x \right)=x\sqrt{2x+5}$$ , where C(x) is

the cost in thousands of dollars and x is the number of units manufactured in the

hundreds. At what rate is cost changing if 200 units are manufactured? What if

400 units are manufactured? How did you arrive at your conclusions?