3. Assume that the Blue Shirts Boutique Shop can purchase shirts for $32 from a local factory, other variable costs amount to $10 per unit. The local factory allows the Shirts Shop to retum all unsold shirts and receive a full $32 refund per pair of shirts within one year. The average selling price per shirts is $70, total fixed costs amount to $84,000 and 2,500 units are sold. What is the contribution margin per unit? What is the total contribution margin when 2,500 shirts are sold? a. $32; 84,000 b. $42; $70,000 c. $28; 70,000; d. $32; 70,000