12. The population increase causes a rightward shift in the demand curve for potatoes, and the development of the higher yielding variety causes a rightward shift in the supply curve for potatoes. The equilibrium quantity of potatoes goes up, but the equilibrium price may go either down or up 13. The discovery of the cold-fighting property causes a rightward shift in the demand curve for apples, and the fungus causes a leftward shift in the supply curve. The equilibrium price of apples will rise, but the equilibrium quantity may go either down or up 14. Since butter and corn are complements, an increase in the price of butter will cause the demand curve for corn to shift leftward. The fertilizer price decrease causes the supply curve for corn to shift rightward. The equilibrium price of corn falls, but the equilibrium quantity may go either down or up 15. Since both the demand and supply curves for tofu have shifted outward equilibrium quantity of tofu sold is higher than before. The equilibrium price m be either higher (left panel)or lower(right panel)12. The population increase causes a rightward shift in the demand curve for potatoes, and the development of the higher yielding variety causes a rightward shift in the supply curve for potatoes. The equilibrium quantity of potatoes goes up, but the equilibrium price may go either down or up. 13. The discovery of the cold-fighting property causes a rightward shift in the demand curve for apples, and the fungus causes a leftward shift in the supply curve. The equilibrium price of apples will rise, but the equilibrium quantity may go either down or up. 14. Since butter and corn are complements, an increase in the price of butter will cause the demand curve for corn to shift leftward. The fertilizer price decrease causes the supply curve for corn to shift rightward. The equilibrium price of corn falls, but the equilibrium quantity may go either down or up. 15. Since both the demand and supply curves for tofu have shifted outward, the equilibrium quantity of tofu sold is higher than before. The equilibrium price may be either higher (left panel) or lower (right panel)