Having Worked for Many of the Firms in the Petroleum

Having worked for many of the firms in the petroleum industry, you know that the price elasticity of demand for a representative firm is about -1.25.Moreover, a recent report from an economist in your office revealed that the price elasticity of demand for the petroleum products sold by your firm is -1.5.Based on this information you know that Rothschild index is

A) 0.833.
B) 1.20.
C) -1.20.
D) -0.833.