Assist please...it related to taxation in America

Question Three: (6 points) You bought equipment for $10,000 and fully depreciated this equipment. You sell the equipment for $4,000 this year. What happens? Assume instead that the equipment is sold for $12,000. What happens? Question Four: (6 points) You bought a building for $100,000 and fully depreciated this building. You sell the building for $40,000 this year. What happens? Assume instead that the building is sold for $120,000. What happens