Hi, all I have struggled with this part was that why is X and Y equals to 64? Please explain!

(h) Sketch the graph of a typical iso-Y section: that is, the curve showing how U varies as consumption of X increases with consumption of Y held constant. Similarly, sketch the graph of an iso-X section. The curve giving U as a function of X with Y constant (iso-Y section) is increasing (ox > 0) and concave (272 0) and concave (ayz 0 = An increase in the consumption of Y has a positive impact on the marginal utility of X @MUY = ay axay azu = 2 x my i > 0 = An increase in the consumption of Y has a positive impact on the marginal utility of Y.M4. Consider an individual's utility function of the Cobb-Douglas form: 1 E U=X3Y3 Where U is an index of the individual's utility and X and Y are the weekly quantities of the two goods consumed. (Note: if you haven't taken economics before, some of these terms may be unfamiliar. But utility and in difference curves are due to be discussed in the Week 4 lectures, so you can always postpone this question for a few days if you're confused.)