7. The accompanying computer excel output (please see attachment on Blackboard) provides details of data and analysis on the topic of firm sales. A manager wishes to study the relation between sales (Y), advertising spending (X1, in $), firm size (X2), and financial leverage (X3).\ \ \ The output includes a listing of all 60 observations; and, the results of a regression analysis that uses firm sales as the dependent variable, and advertising, firm size, and financial leverage.