Suppose there are nine sellers and nine buyers, each willing to buy or sell one unit of a good, with values {$10, $9, $8, $7, $6, $5, $4, $3, $2}. Assuming no transactions costs and a competitive marketWhat is the optimal bid-ask spread?a. $2 bid; $10 askb. $4 bid; $8 askc. $5 bid; $7 askd. $6 bid; $6 ask5.Now suppose that competition among several market makers forces the spread down to $2. How many goods are traded?