Question

The cost of producing x units of particular commodity is 𝐶(𝑥) = 1 3 𝑥 2 + 4𝑥 + 53 dollars, and the production level t hours into a particular production run is 𝑥(𝑡) = 0.2𝑡 2 + 0.03𝑡 units. At what rate is cost changing with respect to time after 4 hours