For what formula can I use to find out the solution?

Suppose that the demand for sweatshirts at the university bookstore is given by: P = 40 - 0.2Q a) Using the point elasticity method, the price elasticity of demand at a price of $2 is (round to two decimal places if applicable) b) Using the point elasticity method. the price elasticity of demand at a price of $8 is (round to two decimal places if applicable) c) Using the point elasticity method, the price elasticity of demand at a price of $12 is round to two decimal places if applicable). d) At the price of $8, is the demand for sweatshirts elastic, unit-elastic or inelastic? (just type "elastic" "unit-elastic" or "inelastic") e) If the goal of the university is to increase total revenue, would you recommend increasing the price of a sweatshirt from $8 to $12? (Answer "Yes" or "No" in the space provided)