ABU Co. has several products, each with a different contribution margin ratio. If the same number of units were sold in July as in June, but the sales mix changed: A. operating income would be the same in June and July. B. fixed expenses in July would be in a different relevant range than in June. C. the company's overall contribution margin ratio would be the same in June and July. D. total contribution margin in July would be different from that in June.