I do not understand how this answer cam to be. Please explain step by step. What happened to 100 in TC when getting MC? How did .02Q² become .04Q in MC?

Question:

The total revenue and total cost function that faces firm A are:

TR=10Q

TC=100+5Q+0.02Q^2 (Note: Q^2 is q-squared)

What is firm's A marginal cost (MC)?

Select one:

a. 50-0.04Q

b. 5+4Q

c. 5+0.04Q

d. 50+0.04Q