Assume that a firm uses big data to estimate the price elasticity of demand for two different groups of consumers who buy its product. The price elasticity of demand for the first group is estimated to be $-1\mathrm{.}5$ and the price elasticity of demand for the second group is estimated to be $-0\mathrm{.}6.$ To increase the firm's revenue which group should be charged a higher price?Briefly explain your answer.