1. Use the graph to answer the question that follows. (3 points)

S Price ($) T U $600 V W $400 - - X - D 15,000 20,000 QuantityS=MSC=MPC Price ($) P + - P, - MSB D=MPB Quantity Q Q1 Q2 Q3\fPrice ($) 5 S 4 3.5 + 3 2 D 360 540 QuantityS Price ($) 5 S 4 3.5 + 3 2 D 360 540 Quantity100 80 60 Percentage of Income 40 2020 2015 20 -l- - 2010 0 20 40 60 80 100 Percentage of Households