A study was conducted to test the effect of product price level and display type on supermarket sales. At one supermarket, the price level $($regular$,$ reduced price, and at cost to supermarket$)$ and the display type $($normal display space, normal display space plus end of aisle display, and twice the normal display space$)$ were varied to determine if they had any effect on the weekly sales of a particular supermarket product. Each combination of price and display was used three times over the course of the experiment.

a$)$ Identify the treatments used in this experiment.

The three display types used by the supermarket.

The supermarket.

The three price levels used by the supermarket.

The nine combinations of price levels and display types used by the supermarket.

The weekly sales for each of the weeks the product is available.

b$)$ Identify the response variable for this experiment.

The combination of price level and display type for each week.

The supermarket.

The normal display space, the normal display space and end of aisle display, or twice the normal display space.

The weekly sales for each of the weeks the product is available.

The price level of the product.