Suppose That There Are Only Three Consumers of a Product

Suppose that there are only three consumers of a product. At a price of $6 per unit, the first consumer would buy 12 units of the product, the second consumer would buy 8 units, and the third consumer would buy 3 units of the product. If you drew a market demand curve for this product, the quantity demanded at a price of $6 would be

A) 23 units.
B) 20 units.
C) 12 units.
D) 11 units.