Worldwide annual sales of smartphones in over a 5 year period were projected to be approximately 9 = -10p + 4,460 million phones at a selling price of $p per phone. (a) Obtain a formula for the price elasticity of demand E. (b) In one particular year the actual selling price was $271 per phone. What was the corresponding price elasticity of demand? Interpret your answer. (c) Use your formula for E to determine the selling price that would have resulted in the largest annual revenue. What, to the nearest $10 million, would have been the resulting annual revenue