2.4 A sporting goods store has estimated the demand curve for a popular brand of running shoes as a function of price. Use the diagram to answer the questions that follow. 70 Price per pair ($) E Demand 10 0 100 200 300 400 500 600 Shoe sales per week a. Calculate demand elasticity using the midpoint formula between points A and Il, between points C and D, and be tween points E and F. b. If the store currently charges a price of $50, then increases that price to $60, what happens to total revenue from shoe sales (calculate PX Q before and after the price change)? Repeat the exercise for Initial prices being decreased to $40 and $20, respectively. C. Explain why the answers to a. can be used to predict the answers to b