Don't answer by pen paper

As the new semester begins, students need to purchase the textbooks for Microeconomics. The book market at PKU is a competitive market with a demand function of D(P) = 200 - 15P and a supply function of S(P) = 5P. (a) What is the price and quantity of books traded in equilibrium? (2 points) (b) What are the consumer's price and seller's price in equilibrium when there is a quantity tax of 4 yuan on each book? What is the quantity of books traded? (4 points) (c) What is the tax incidence? (2 points) (d) What is the deadweight loss caused by the tax? (2 points)