On a graph we draw a consumer's budget constraint, measuring the number of apples on the horizontal axis and the number of light bulbs on the vertical axis. If the slope of the budget constraint is -2, then Group of answer choices a. an apple costs twice as much as a light bulb. b. the opportunity cost of a light bulb is 2 apples. c. the opportunity cost of an apple is one-half of a light bulb. d. All of the above are correct