Worldwide annual sales of smartphones over a two year period were approximately q = -4p + 3,010 million phones at a selling price of $p per phone. (a) Obtain a formula for the price elasticity of demand E. E = (b) In one of the years the actual selling price was $305 per phone. What was the corresponding price elasticity of demand? (Round your answer to two decimal places.) E = Interpret your answer. The demand was going |---Select--- by about % per 1% increase in price at that price level. (c) Use your formula for E to determine the selling price that would have resulted in the largest annual revenue. What would have been the resulting annual revenue? (Round your answer to two decimal places.) billion LA