Calculate the price elasticity of demand for a commodity when its price increases by 25 % and quantity demanded falls from 150 units to 120 units.
a. Arrange the following coefficients of price elasticity of demand in ascending order: -0.87, -0.53, -3.1, -0.80
b. Comment upon the degree of elasticity of demand for commodity X, if the price of the commodity falls from Rs 28 per unit to Rs 23 per unit and its quantity demanded rises from 50 units to 100 units.