$5.$ When evaluating a company's sales performance, management should:

A$.$ Determine which marketing unit is weak and why it is weak, before recommending action to improve the situation.

B$.$ Prepare a complete marketing audit.

C$.$ Not make a sales volume analysis unless it is followed by a marketing cost analysis.

D$.$ Investigate the $80-20$ principle.

E$.$ Not go into great detail as long as sales are increasing.