问题如下图：
选项：
A. 
B. 
C. 
解释：
变形后的公式，是-5✖️（p/Q）这里的p和q根据老师讲课的说法，都应该是变化前后的平均值吧？为什么现在可以直接把某一个点的值35、225带入呢？
NO.PZ2017100901000002 问题如下 The manfor membership a lochealth club is terminethe following equation:Qm = 400 − 5 Phmwhere Qm is the number of health club members anPhm is the priof membership. If the priof health club membership is $35, the prielasticity of manis closest to: A.–0.778. B.–0.500. C.–0.438. A is correct.Inserting the priof $35 into the manfunction, quantity manis calculateasQm = 400 − 5 (35) =225a priof $35 per health club membership, the elasticity of manis Prielasticity of man= (∆Qm / ∆Phm)× ( Phm/Qm)Prielasticity of man= –5 × (35/225) = –0.778考点点弹性解析当价格等于35的时候，依据需求函数Qm = 400 − 5 Phm和点弹性公式(∆Qm / ∆Phm)× ( Phm/Qm)可得点弹性数值– 5 × (35/225) = – 0.778 RT，谢谢老师
题目写错了，400前不应该有负号
