单选题
The price of product Z decreased from $2.50 per unit to 2.00 per unit. Since the price decreased, demand has gone up from 3 million units to 4 million units. Calculate the price elasticity of demand and determine if the demand is elastic or inelastic.（ ）
【正确答案】
A
【答案解析】
Percentage change in quantity=[(4-3)]/[(4+3)/2]=1/3.5=0.286=28.6%.
Percentage change in price=[(2-2.5)]/[(2+2.5)/2] =-0.5/2.25=-0.222=-22.2%.