In which of the following ways can a firm estimate its marginal cost of production? Select a Choice Below current question choices OptionA By calculating the difference between the quantity of an input and the price of the input, employed by the firm OptionB By calculating the difference between the total cost of production and the total revenue of the firm OptionC By calculating the slope of the total cost line at a given level of output OptionD By calculating the sum of the fixed cost and the variable cost of the firm at a given level of output