I met this question and I am totally confused by the way the answer is worked. The Break even point is derived at by dividing Total Contribution Margin by CM per composite unit. Answer choice D (10,500 units) was chosen as the best answer Why Total contribution margin and not Fixed cost divided by CM per composite unit? I chose B (6,000) because I used the Fixed cost formula.

Here is the question:

Wren Co. manufactures and sells two products with selling prices and variable costs as follows:

A B

SELLING PRICE $18.00 $22.00

VARIABLE COSTS $12.00 $14.00

WREN'S TOTAL ANNUAL FIXED COSTS ARE $38,400. WREN SELLS FOUR UNITS OF A FOR EVERY UNIT OF B. IF OPERATING INCOME LAST YEAR WAS $28,800, WHAT WAS THE NUMBER OF UNITS WREN SOLD?

A. 5,486

B. 6,000

C. 9,600

D. 10,500

ANY HELP WOULD BE APPRECIATED! THANK YOU AND BE SAFE.