Identify the predictor variable x and the response variable y in each of the following situations.
(a) The state highway department wants to study the relationship between road roughness and a car's gas consumption.
(b) A concession salesperson at football games wants to relate yearly total fall sales to the number of games the home team wins.
(c) A sociologist wants to investigate the number of weekends a college student goes home in relation to the trip distance.