Can somebody help me with this question. "A farmer wants to test the effects of fertilizer on the growth of his bean plants. He gives a half acre of bean plants fertilizer once a week and gives another half acre of bean plants just water. Both areas of bean plants in the garden receive the same amount of sunlight and the farmer uses the same type of soil and species of bean plant. They also receive the same amount of water daily. The farmer harvests beans from the plants every Friday for two months in both areas. He counts the number of beans he harvests from each area and records them on Friday. WHAT IS THE CONSTANT IN THIS EXPERIMENT? WHAT IS THE CONTROL IN THIS EXPERIMENT?"