The following function describes Dwight’s demand for ink pens: where QN is the quantity demanded for pens, PN is the price of pens, PP is the price of pencils, and I is Dwight’s income (in thousands of dollars). If the supply curve of pens is . What is the price elasticity of demand at equilibrium? What is the cross-price elasticity for pencils at equilibrium? What is the income elasticity of demand at equilibrium?