O Required information 305 Knowledge Check 01 Product A Product B Selling price per unit $ 20 $ 15 Variable cost per unit 12 9 Contribution margin per unit $ 8 $ 6 Labor time 4 minutes 2 minutes Roberto, Incorporated manufactures products A and B. Both products have a contribution margin ratio of 40%. What is the contribution margin per unit of the constrained resource for product B, if labor time is the constrained resource? O $2 per minute O $3 per minute O $6 per minute O $8 per minute