Tully is a graduating high school senior deciding between three alternative combinations of education- work options. He could start working immediately and earn $30,000 working in a burrito truck in period one. His salary would increase to $60,000 in period 2 as he would become chef, and then fall in period 3 to $50,000 as he would become too physically tired to work too much in the kitchen. His first alternative is to spend $15,000 to attend Da-Lousy University for economics and earn an undergrad degree in period 1. Upon obtaining his degree he would earn $80,000 as an economist for periods 2 and 3. The final option is for Tully to complete a doctorate degree in economics after finishing his undergrad degree. There would be no direct costs as he would get scholarships, but he could not work in period 2 while he completed his PhD. After finishing his PhD he would earn $200,000 as an Econ Prof at Kings University in period 3. His interest rate is 15 percent per period. What should Tully choose to do? How does the discount rate influence his decision? Carefully explain.