This is an Experimental and Observational Studies question

What are the effects of repeated exposure to an advertising message? An experiment investigated this question by using undergraduate students as subjects. All subjects viewed a 40 minute television program that included ads for a 35mm camera. The subjects were assigned to two groups, one group saw the commercial once during the program, the other saw it during every commercial break. After viewing, all subjects answered questions about their recall of the ad, their attitude toward the camera, and their intention to purchase it. Part a: Is this an experimental study or an observational study? Explain. Part b: What are the subjects of the study? Part c: What are the treatments? Part d: What is the response variable? Part e: What variables need to be controlled