For the total cost function $$C = 1000 + 120x + 14x^{2} + x^{3}$$ find marginal cost function.

A

$$1000 + x + 14x^{2} + 3x$$

B

$$120 + 28x + 3x^{2}$$

C

$$28x + 3x^{2}$$

D

$$120x^{2} + 14x^{3} + x^{4}$$