A. The unit contribution margin is units sales - unit variable costs. The sales price of $90 Less variable costs per unit of $70 equals a unit contribution margin of $20. If 2 units are produced and sold, the total contribution margin would be $20 × 2 units = $40 total contribution margin.

B. This is the unit variable costs. The total contribution margin equals total sales minus total variable costs ($180 - $140 = $40).

C. This is fixed costs on a per unit basis. The total contribution margin equals total sales minus total variable costs ($180 - $140 = $40).

D. The total contribution margin equals total sales minus total variable costs ($180 - $140 = $40).