A single mother has y=$400 in non-labour income and w=$15 per hour in labour income. She has up to 100 hours available from which she can decide how much to work. The tax rate is zero. a) Write down the budget constraint and draw it on a graph. Make sure to label the axes and intercept correctly. Assume that the mother is already working 40 hours per month. Show the indifference curve and the optimal point on the graph