Question 24 (1 point) Which of the following statements about Production Possibility Frontiers (PPF) in a two good economy are always TRUE? I. A PPF is concave (bowed outward) when the opportunity cost of producing a good increases as more is produced II. A PPF is concave (bowed outward) when the opportunity cost of producing a good decreases as more is produced III. A PPF is straight when the opportunity cost of producing a good is 0 IV. A PPF is straight when the opportunity cost of producing a good is constant O1., III. OI., IV. OIL., IV. OIL