Describe the demand model and its purpose. Describe the supply model and its purpose. Some important questions need to be answered in your description. Why is the demand curve sloped down and what law describe this downward slope? Why is the supply curve upward sloping? What is the difference between change in demand and change in quantity demanded? List the determinants (demand shifters) that will shift the demand curve, "change demand". List the supply shifters. If demand and supply shifters shifts the demand and supply curve, what is the only variable change that will cause a movement along the curves instead of a shift in the curves (variables to consider is price, quantity, demand or supply shifters).