The demand function for a transit system can be represented by a straight line connecting fare per person and ridership. Observations made on this system resulted in the following: When the fare was $1.5 per ride, the ridership per hour was 2000; when the fare was raised to $2 per ride, the ridership dropped to 1000. What is the equation of the demand function? What would be the patronage if the fare was (a) 50¢ per ride; (b) zero?