Suppose there are 11 buyers and 11 sellers, each willing to buy or sell one unit of a good, with values {$14, $13, $12, $11, $10, $9, $8, $7, $6, $5, $4,}. Assume no transaction costs and a competitive market. At the optimal bid, ask spread, what is the total profit that the market maker makes?

Select one:

a.

$8

b.

$12

c.

$18

d.

$20