2a.) Demand curves illustrate the relation between PX and QDx, thus implicitly holding PA, PB, and Y constant. As an example, let QDx = 100 - 8*PX + 2*Y + 5*PA - 10*PB with PX = 5, Y= 20, PA = 2, and PB = 7. Pick two other values for PX, calculate the subsequent QDx, and draw a demand curve.

b.) Returning to the original values in this question, allow Y to take a different value. Calculate QDx and (remembering that PX is unchanged) draw that point on your graph from 2a. Then, using the values for PX you chose in part a of this question (and the new value for Y), calculate the subsequent values for QDx and draw the new D.

c.) Establish a rule for what causes a movement along D and what requires a shift in D.