a. Suppose the monthly income of an individual increases from Rs 20,000 to Rs 25,000 which increases his demand for clothes from 40 units to 60 units. Calculate the income elasticity of demand.

b. Assume that a business firm sells a product at the price of Rs 500. The firm has decided to reduce the price of the product to Rs 400. Consequently, the demand for the product is raised from 20,000 units to 25,000 units. Calculate the price elasticity of demand.