You give up a full time salary of 45,000 a year to go to school for 2 years the total cost of going to school is 30,000, if want to be able to recover your investment in 5 years or less what is the minimum salary you would need to earn upon earning your degree?

I would say that this person has lost out on 2 years salary while in school plus 5 year repayment period. Total amount divided over 5 years is:( (2+5)(45,000) + 30,000 ) / 5 = (7(45,000)+30,00)/5 = 69,000 salary