#### Answer

Total cost is the sum of the market value of all the inputs that a firm uses in production.
TC=FC+VC;
where TC is Total Cost, FC is fixed costs and VC is variable costs.
Average total cost is the total cost divided by the quantity of output.
ATC=TC/Q;
where ATC is average total cost, TC is total cost and Q is output.
Marginal cost is the increase in total cost that arises from an extra unit of production.
MC=ΔTC/ΔQ,
where MC is marginal cost, ΔTC is the change in total cost and ΔQ is the change in output.

#### Work Step by Step

From a firm’s total cost, we can derive the average total cost and the marginal cost. For a typical firm, marginal cost rises with the quantity of output. Average total cost first falls as the output increases, but then rises as the output increases further.