Assume the individual has a fixed budget of 24 per week to spend on burgers, and the current price of cheeseburgers and chicken burgers is 3.00, and that a consumer buys 4 of each type of burger. Now assume that the price of cheeseburgers falls to 2. Using the concept of the 'income' and 'substitution' effect, explain why the demand for cheeseburgers rises to 6.