For alarm clock supply, price rises from $8 to $9 and quantity supplied rises from 50 to 70 units. Using the midpoint method, what is the price elasticity of supply over this interval?

1. Percentage change in quantity: (70 minus 50) divided by the average of 70 and 50, which is 60, times 100. 2. That gives 20 divided by 60, times 100, which is about 33.3 percent. 3. Percentage change in price: (9 minus 8) divided by the average of 9 and 8, which is 8.5, times 100. 4. That gives 1 divided by 8.5, times 100, which is about 11.76 percent. 5. Price elasticity of supply equals 33.3 divided by 11.76, which is about 2.83. 6. Since 2.83 is well above one, supply is elastic over this interval. 7. Option C's exactly 1.00 would require the two percentage changes to be equal, and they are not. 8. Options D and A belong to other elasticity calculations, not this alarm clock interval. _Source: OpenStax Principles of Microeconomics for AP Courses (CC BY 4.0), Ch 5 "Elasticity", section 5.1 | Price Elasticity of Demand and Price Elasticity of Supply_