Which of the following is true of differential income (or loss)?

a. It is the amount of increase or decrease in cost that is expected from a course of action as compared to an alternative.

b. It is the difference between differential revenue and differential cost.

c. It is the amount of increase or decrease in revenue that is expected from a course of action as compared to an alternative.

d. It is the difference in incomes or losses of the current year and the previous year.