The Formula for the Cross-Price Elasticity of Demand Can Be $\eta$

The formula for the cross-price elasticity of demand can be written as:

A) $\eta$ _XY = ( $\Delta$ Q_X / $\Delta$ P_Y) (P_Y / Q_X)
B) $\eta$ _XY = ( $\Delta$ P_Y / $\Delta$ Q_X) (P_Y / Q_X) .
C) $\eta$ _XY = ( $\Delta$ P_Y / $\Delta$ Q_X) (P_Y / Q_X)
D) $\eta$ _XY = ( $\Delta$ P_Y / $\Delta$ Q_X) (Q_X / P_Y) .
E) none of the above.