Sales increases

QUESTION: Chapter 3; Question 5 An automobile manufacturer observes the demand for its brand increasing as per capital income increases. Sales increases also follow low interest rates, which ease credit conditions. Buyer purchase behavior is seen to be dependent on age and gender. a. If sales and per capital income are positively related, classify all variables as dependent, independent, moderating, extraneous, or intervening. b. Comment on the utility of a model based on the hypothesis.