Answer: Elasticity of demand mesures the responsivness of quantit demanded to a change in the price of the product. It is calculated as,
![e=(Change in Q)/(Original Quantity) * (Original Price)/(Change in Price)](https://img.qammunity.org/2019/formulas/business/college/k5odijw384b3lv5zu18685y7er5tjhtftz.png)
a. P1 = $160 , P2= $140, Q1=80, Q2= 120
e=
![image](https://img.qammunity.org/2019/formulas/business/college/5vpjo8nh4wcrurvebwnwwtrc4bx8m8t4u5.png)
b. P1 = $140 , P2= $160, Q1=120, Q2= 80
e=
![image](https://img.qammunity.org/2019/formulas/business/college/wg56qgbkhmsogj5u2rif874e07znv1scow.png)
c. Mid-point method is given by
![e=(Q2-Q1)/(Q1+Q2/2) * (P1+P2/2)/(P2-P1)](https://img.qammunity.org/2019/formulas/business/college/spyc2conzp4wlm1o8k8cti1lfc9qd48rcs.png)
So, we have
![image](https://img.qammunity.org/2019/formulas/business/college/7g5apmyi8gy8uvazlvpwtf1fzn70c3ces2.png)
d. P1=$40, P2= $20, Q1= 320, Q2= 360
![image](https://img.qammunity.org/2019/formulas/business/college/6bh4t85npxgr6fjp2oeabm6q33k3gjb0k7.png)
e. P1=$20, P2= $40, Q1= 360, Q2= 320
![image](https://img.qammunity.org/2019/formulas/business/college/4c4m2ckdcw8qpstonje9ma83z9bewbgfs0.png)
f. [tex] e= \frac{360 - 320}{360+320/2} * \frac{40+20/2}{20-40}
=\frac{40}{340} * \frac{30}{-20}
= - 0.17