Does adding fertilizer affect the productivity of tomato plants? How about the amount of water given to the plants? To answer these questions, a gardener plants 24 similar tomato plants in identical pots in his greenhouse. He will add fertilizer to the soil in half the pots. Also, he will water 8 of the plants with 0.5 gallon of water per day, 8 of the plants with 1 gallon of water per day, and the remaining 8 plants with 1.5 gallons of water per day. At the end of 3 months, he will record the total weight of tomatoes produced by each plant.

(a) List the factors in this experiment and the number of levels for each factor.

(b) If the researchers used every possible combination of levels to form the treatments, how many treatments were included in the experiment?

(c) List all the treatments.