Answer: buying lobsters in Maine and selling them in Massachusetts. This action would decrease the price of lobster in Massachusetts.
Explanation:
A lobster in Maine is sold at $10 while the same type of lobster is sold at $30 in Massachusetts. People would make a profit when they buy the lobster at $10 I'm Maine and sell at a price lower than $30 in Massachusetts.
The lobster is cheaper in Maine, so the logical thing to do is to buy at w country where it is cheaper and sell at Massachusetts. This will help reduce the price in Massachusetts to a price lower than $30 and the seller makes profit.