Answer: Buys the excess supply of milk.
Step-by-step explanation:
Given that,
Equilibrium price of milk = $3 per gallon
Federal government sets the market price = $4 per gallon
The government have to buy excess supply of milk and remove it from the market if Fed wants to keep the price of milk at $4 per gallon. Once the excess supply of milk extracted from the market then as a result equilibrium price of milk rises to $4 per gallon.