Referencing Styles : Harvard Consider the following regression model between the dependent variable, SALES (reflecting monthly sales, in thousands of dollars) and independent variable, ADVERTISING (representing the monthly advertising expenditure, in thousands of dollars): Estimated SALES = 4.2 + 2.6 ADVERTISING. The value 4.2 in the above regression line represents: Select one: a. the proportion of the variation in SALES explained by variation in ADVERTISING b. the change in SALES, on average, following a unit increase in ADVERTISING c. a ratio of SALES over ADVERTISING as a percentage d. the estimated value of SALES when ADVERTISING is zero