Combine the two Postal Service events: higher labor compensation shifts supply left, and the shift toward digital messages shifts demand left, both at the same time. What can be said for certain about the overall change in equilibrium quantity, and about the overall change in equilibrium price?

1. The supply shift left pushes quantity down, and the demand shift left also pushes quantity down. 2. Since both effects on quantity point the same direction, equilibrium quantity definitely falls. 3. The supply shift left pushes price up, but the demand shift left pushes price down, so the two price effects fight each other. 4. Without knowing which shift is larger, the net effect on price cannot be determined from the model alone. 5. Option B is wrong because a leftward supply shift alone would raise price, not lower it, so the two effects do not simply add. _Source: OpenStax Principles of Macroeconomics for AP Courses (CC BY 4.0), Ch 3 "Demand and Supply", section 3.3 | Changes in Equilibrium Price and Quantity: The Four-Step Process_