At a Price Of $\$ 2.75$ Per Gallon, the Average Weekly Demand by Consumers for Gasoline

Multiple Choice

At a price of $\$ 2.75$ per gallon, the average weekly demand by consumers for gasoline is 45 gallons. If the price rises to $\$ 2.85$ , the weekly demand drops to 41 gallons. Assuming demand is linear, let $Q=b+m p$ , where $Q$ is the weekly quantity of gasoline demanded and $p$ is the price per gallon. What is the economic interpretation of the $p$ -intercept?

A) The the price at which no gasoline will be demanded.
B) The number of gallons demanded if gas were free.
C) The amount the demand decreases if the price rises $\$ 1$ .
D) The amount the price decreases if the demand is increased by 1 gallon.