During the summer months Terry makes and sells necklaces on the beach. Last summer he sold the necklaces for $10 each and his sales averaged 20 per day. When he increased the price by $1, he found that the average decreased by two sales per day.

(a) Find the demand function (price p as a function of units sold x), assuming that it is linear. p(x) =

(b) If the material for each necklace costs Terry $6, what should the selling price be to maximize his profit? $___ per necklace