For Each of the Following Scenarios Indicate Which Is the Predictor

For each of the following scenarios indicate which is the predictor variable and which
is the response variable.
a. A supermarket chain gathers data on the amount they spend on promotional material
(specials, coupons, etc.) and sales revenue generated each quarter.
b. Government-sponsored research investigated the relationship between number of hours
individuals spend on the Internet and age.
c. A real estate association conducted a study on home prices and economic strength for
different regions of the United States.