Explain the term Price Elasticity of Demand . When the price of a commodity rises from $10 to $20, the quantity demanded falls from 16 units to 14.

1. Explain the term Price Elasticity of Demand. When the price of a commodity rises from $10 to $20, the quantity demanded falls from 16 units to 14. Calculate the price elasticity of demand using the average price method.
2. What are the principal determinants of the Price Elasticity of Demand? Provide an example in each case.
3. Explain the Substitution and Real Income Effects of a price change. Provide an example from your own experience of grocery shopping.

Please provide citations.