2.11. Suppose that the quantity of corn supplied depends on the price of corn (P) and the amount of rainfall (R). The demand for corn depends on the price of corn and the level of disposable income (I). The equations describing the supply and demand relationships are Qs ! 20R " 100P and Qd ! 4000 # 100P " 10I.

a) Sketch a graph of demand and supply curves that shows the effect of an increase in rainfall on the equilibrium price and quantity of corn.

b) Sketch a graph of demand and supply curves that shows the effect of a decrease in disposable income on the equilibrium price and quantity of corn.