i not really know how to do the third question , can you plz help the third question. it is hard for me :( just give me the explanation, don't worry about the word limit. thanks.

Consider a competitive economy in which there are only two goods, good a and good b. Aggregate demand for good a is: QE = 400 4019a (1) Aggregate supply for good a is: Q3 = 10Pa (2) Aggregate demand for good b is: E = 600 1013b (3) Aggregate supply for good b is: Q3 = ZOPb (4) I. for each good i, where i E {(1, b}, nd the competitive equilibrium price P: and the competitive equilibrium quantity Q15; 11. for each good i, nd the price elasticity of demand and the price elasticity of supply at Pf, which we respectively call I]? and \"is ; III. In this economy, the government wants to raise B = 1000 AUD while minimising the deadweight loss of the taxes introduced. Hence, the government needs to solve the Ramsey problem shown below. Solve the Ramsey problem and briey comment on the results (less than 300 words). If you choose to solve it using the Lagrangian method, proceed by finding the FOCs as if you were solving a maximisation problem: the calculations are exactly the same; min nana X 7 Qa Qb Ta, Tb 2 (na - na) X P* + 2 (16 - no X THX P* (5) subject to (QP&Ta +Qjp;Tb) =R (6) IV. What is the impact of a change in Ta on Pi