Use the graph to answer the question that follows. A graph labeled price on the vertical axis and quantity on the horizontal axis. A line labeled D equals MPB slopes downward from left to right. A parallel line labeled MSB is to the right of the first line. A third line, labeled S equals MSC equals MPC, slopes upward from left to right and intersects each of the first two lines. A horizontal line labeled P1 that intersects with the line labeled MSB and the line labeled S equals MSC equals MPC at a quantity Q3. A horizontal line labeled P2 is below P1 and intersects with the line labeled S equals MSC equals MPC and D equals MPB at quantity Q2. A vertical line labeled Q1 intersects with the line P1 at D equals MPB. A vertical line labeled Q2 is to the right of Q1 and intersects with the line D equals MPB and S equals MSC equals MPC at price P2. A vertical line labeled Q3 is to the right of Q2 and intersects with the line MSB and S equals MSC equals MPC at P1. A vertical line labeled Q4 is to the right of Q3