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10. Johnson Company operates two plants: Plant A and Plant B. Johnson Company reported for the year just ended a contribution margin of $55,000 for Plant A. Plant B had sales of $200,000 and a contribution margin ratio of 50%. Net operating income for the company was $10,000 and traceable fixed costs for the two plants totalled $50,000. What were Johnson Company's common fixed costs for last year? a. $75,000. b. $95,000. C. $45,000 d. $55,000