Suppose that when the price of good X falls from $60 to $48, the quantity demanded of good Y falls from 10 units to 8 units. Using the midpoint method, the cross-price elasticity of demand is
a.-1.0, and X and Y are complements.
b.-1.0, and X and Y are substitutes.
c.1.0, and X and Y are complements.
d.1.0, and X and Y are substitutes.