A market is comprised of three groups of consumers, each with different demand curves and different number of consumers: Group 1 has 150 consumers, each with a demand curve, p ( q) =25 - 0.1q. Group 2 has 100 consumers, each with a demand curve, p ( q) = 25 - 0.5q. Group 3 has 50 consumers, each with a demand curve, p ( q) = 25 - q. The demand function (not the inverse demand/demand curve) for the market, $$ Q(p) = _. $