Using the Midpoint method:In the above table, the cross price elasticity of demand for good Z with good Y when PY rises from $15 to $18 is

Month PX QX PY QY PZ QZ Jan $10 100 $20 50 $25 200 Feb 10 90 18 60 25 225 Mar 10 70 15 90 25 275 Apr 12 50 15 100 25 290 May 15 25 15 120 25 320