A consumer is paid each week 4 units of x1 and 4 units of x2 which she may consume directly or trade with other customers at the going rate of exchange. In the first week she trades and finally consumes 5 units of x1 and 3 units of x2. In the second week there is a new rate of exchange and she finally consumes 6 units of x1 and 1 unit of x2. Assuming her tastes remained unchanged for these two weeks: (i)in which week is the consumer better off? (ii) In the third week the exchange rate is such that she could consume 5.5 units of x and 2 units of x2, but she prefers instead to consume her initial bundle of 4 units each. Must it be concluded that her tastes have now changed? You must use the Weak Axiom of Revealed Preference to justify your answer.