Use the following table to answer the following questions.

Price of T-shirts Quantity demanded when the average income is $20 000 Quantity demanded when the average income is $30 000 4 3000 5000 5 2400 4200 6 1600 3000 7 800 1800

a) Calculate the price elasticity of demand when the price of a T-shirt rises from $5 to $6 and the income is $20 000.

Also calculate it when the income is $30 000.

b) Calculate the income elasticity of demand when the price of the average income rises from $20 000 to $30 000 and the price of a T-shirt is $4. Also calculate it when the price is $7.