You decide to clean the bathroom. You notice that the show is covered in astange green slime. You try get rid of this slime by adding lemonade juice. You spray half of the shower with lemonade juice and spray the other half of the shower with water. After 3 days of spaying equal amounts 3 times a day, there a day, there is no change in the appearance of the green slime on either side of the shower. What is the independent variable.