Straight line Production Possibilities Frontier for Souvenirs and Restaurant Meals with the following points: (0 souvenirs, 12 restaurant meals); (9 souvenirs, 6 restaurant meals); (18 souvenirs, 0 restaurant meals) Refer to the diagram. If society is currently producing 0 units of souvenirs and 12 units of restaurant meals, what is the opportunity cost of increasing production of souvenirs by one unit