Two consumers, Smith and Jones, have the following demand curves for Podunk Public Radio broadcasts of recorded opera on Saturdays:
a. Smith: PS = 12 − Q
b. Jones: PJ = 12 − 2Q,

where PS and PJ represent marginal willingness-to-pay values for Smith and Jones, respectively, and Q represents the number of hours of opera broadcast each Saturday.
a. If Smith and Jones are the only public radio listeners in Podunk, construct the market demand curve for opera broadcasts.