Mr. and Mrs. Shrek enjoy two goods: the quality and quantity of their children. They each live for 30 years. To have a child, Mrs. Shrek must take off 3 years from work. All of their market earnings are invested in the quality of their children. Mr. Shrek has an annual salary of $40,000, while Mrs. Shrek has an annual salary of $50,000. a. Draw the household budget constraint. b. Illustrate what happens to the budget constraint when Mrs. Shrek's salary increases to $60,000. In terms of income and substitution effects, what happens to their fertility choice? c. Illustrate what happens when Mr. Shrek's salary increases to $60,000. In terms of income and substitution effects, what happens to their choice