15.[3] The price of world crude oil was about $56/b ( b for barrel) in February 2020 and $23/b in April 2020. The amount sold in April was about 15% less than in February. Assume that this change was the effect of a shift in one curve (demand or supply) and a slide along the other curve (which did not shift). Which of the following is more likely correct? Pick the best answer. a. The supply curve shifted due to the war in Afghanistan. b. The supply curve shifted due to the pandemic. c. The supply curve shifted due to another reason. d. The demand curve shifted due to the war in Afghanistan. e. The demand curve shifted due to the pandemic. 16.[5] Use the information in problem 15 to estimate the price elasticity of the curve that did not shift. Show all your steps. The price elasiticity of demand or supply is \% change in quantity divided by % change in price