Knowing that you are a college student majoring in marketing at the local university, your supervisor at the local pizza parlor has asked for your input regarding a research study. She wants to determine which of three new pizza toppings should be added to the menu: broccoli, spam, or pineapple. She plans on promoting broccoli in February, Spam in March, and pineapple in April, and using the number of pizzas ordered with each topping to make her decision. List and briefly describe the extraneous factors that may interfere with the results of her study.