Answer:
Step-by-step explanation:
the own price elasticity of demand calculated with the formula
MR ( marginal revenue ) = P ( equilibrium price ) ( 1 + (1/ ED) where ED is price elasticity of demand
20 = 60 ( 1 + ( 1/ED)
(20 / 60) - 1 = 1 / ED
-0.6667 = 1 / ED
ED = 1 / - 0.666667 = -1.5