Jackfruit Health Food produces health supplements. The marketing manager, Jack, looks after the sales department, which has a team of 5 salespeople who are recruited, managed and trained by Jack. Which of the following is the least suitable benchmark to evaluate Jack's performance? a. Fixed overhead cost in the sales department. b. Costs of sales commission. c. Sales variance based on flexible budget. d. The direct material costs of producing health supplements. e. Budgeted training costs of salespeople