In Example 2.8 we examined the effect of a 20% decline in copper demand on the price of copper, using the linear supply and demand curves developed in Section 2.6. Suppose the long-run price elasticity of copper demand were 0.75 instead of 0.5.
a. Assuming, as before, that the equilibrium price and quantity are P*  $3 per pound and Q*  18 million metric tons per year, derive the linear demand curve consistent with the smaller elasticity.
b. Using this demand curve, recalculate the effect of a 20% decline in copper demand on the price of copper.