The accompanying table shows the price and yearly quantity sold of souvenir T-shirts in the town of Crystal Lake according to the average income of the tourists visiting.

a. Using the midpoint method, calculate the price elasticity of demand when the price of a T-shirt rises from $5 to $6 and the average tourist income is $20,000. Also calculate it when the average tourist income is $30,000.
b. Using the midpoint method, calculate the income elasticity of demand when the price of a T-shirt is $4 and the average tourist income increases from $20,000 to $30,000. Also calculate it when the price is $7.

Quantity of T-shirts demanded when average tourist Quantity of T-shirts demanded when average tourist Price of T-shir $4 income is $20,000 income is $30,000 3,000 2,400 1,600 800 5,000 4,200 3,000 1,800