Over the summer Kathleen sold 1000 9092 jars of jam at outdoor market. She made a $12 profit on each one. She wants to use the profits to buy the ivory 5K piano. She said, since 1000×12 = 12,000 at 1092 is greater than 1000, I know my profits add up to more than 12,000 so I can buy the piano. Does it make sense for Kathleen to find an overestimate or underestimate to decide if she has earned enough money? Why?