Obama Company sells its product for $29 per unit. During 2020, it produced 27500 units and sold 15000 units (there was no beginning inventory). Costs per unit are: direct materials $8, direct labour $7, and variable overhead $6. Fixed costs are: $330000 manufacturing overhead, and $110000 selling and administrative expenses. The per-unit manufacturing cost under variable costing is

a. 21

b. 33

c. 37

d. 43