At $86 , a firm can sell 4,785 stereo earphones (3.5 mm for android). At this price, elasticity is estimated at 2.2. What is the change in total revenue (+ or -) if the firm drops price by 11%? Round your answer to the nearest dollar.

At $170, a firm can sell 18,490 stereo earphones (3.5 mm for android). These are premium earphones, guaranteed for 5 years. At this price, elasticity is estimated at 0.5. What is the change in total revenue (+ or -) if the firm drops price by 11%?

A firm sells mid-range snowboards and estimates its demand curve to be Q = 14,700 - 29(P). Variable costs are $280. At what price does the firm's total contribution margin equal zero?