Concept: Total cost is the complete expense of production at a given output level.Explanation:Total cost is calculated by combining all fixed and variable costs incurred in production.Fixed costs do not change with output, while variable costs change with output.Therefore, the formula is:TC=TFC+TVCHere, TC = total cost, TFC = total fixed cost, and TVC = total variable cost.Adding the total fixed cost to the total variable cost gives the total cost at any output level.Answer: D. Adding up the total variable cost and total fixed cost.