Suppose You Can Write Generic Supply and Demand Curves Such $\mathrm { Q } _ { \mathrm { S } } = \mathrm { A } + \mathrm { BP }$

Suppose you can write generic supply and demand curves such that and .If price must reach a certain level before firms supply anything $\mathrm { Q } _ { \mathrm { S } } = \mathrm { A } + \mathrm { BP }$ , $Q _ { D } = D + C P$ ,A must be.

A) positive
B) negative
C) 0