In each of the following cases, indicate which good you think has a relatively more price elastic demand and identify the most likely reason, in terms of the determinants of the elasticity of demand (more substitutes, greater share of budget, or more time to adjust).
a. Cars or Chevrolets
b. Salt or housing
c. Going to a New York Mets game or a Cleveland Indians game
d. Natural gas this month or over the course of a year