Answer:
1) Sherrod's opportunity cost of cleaning the barhtroom is dusting 2 rooms, because cleaning the bathroom takes him 60 minutes, and cleaning 1 room takes him 30 minutes.
2) His opportunity cost is cleaning half the bathroom. Because he dusts one room in 30 minutes, and takes 60 minutes to clean the bathroom.
3) Clarke's opportunity cost is dusting one room, because it takes him exactly the same time to clean the bathroom (45 minutes).
4) His opportunity cost is cleaning 1 bathroom for the same reason as above.
5) Clarke has absolute advantage in cleaning the bathroom, because it takes him less time to do so than Sherrod. Sherrod has absolute advantage in dusting a room, because it takes him less time to do so than Clarke.
6) Sherrod has the comparative advantage in cleaning the bathroom because his opportunity cost is less. Clarke has the comparative advantage in dusting the room because his opportunity cost is less.
7) Each chore should be done by the person who has the comparative advantage: Clarke should ust the room, and Sherrod should clean the bathroom.