The cost of a meal might affect how customers evaluate and appreciate food. To investigate, researchers worked with an Italian all-you-can-eat buffet to perform an experiment. A total of 139 subjects were randomly assigned to pay either $4 or $8 for the buffet and then asked to rate the quality of the pizza on a 9- point scale. Subjects who paid $8 rated the pizza 11% higher than those who paid only $4. Identify the explanatory and response variables, the experimental units, and the treatments.