Research for 4 questions and provide 1-2 references per question

1 What is the price elasticity of demand for brand name drugs? Is it elastic or inelastic? How about fast food?

2 What is the Income Elasticity of demand for these products? Which one has the higher income elasticity and why?

3 What is the cross-price elasticity of demand (if any) between the main products of the two companies?

4.What about among Pfizer's main products and related products, and among McDonalds' main products and related products?