Let us sum two demand curves to obtain a ‘market' demand curve. We will suppose there are just two buyers in the market. The two demands are defined by: P = 42 - (1/3)Q and P = 42-(1/2)Q.
(a) Draw the demands (approximately to scale) and label the intercepts on both the price and quantity axes.
(b) Determine how much would be purchased at prices $10, $20, and $30.