Wording in our child support agreement states, “The parties shall pay a pro rata share of the final cost of college including college tuition, room, board, books, fees, food based on their respective net incomes during the calendar year prior to the year in which the college expenses are incurred”. What is used to determine “net income”?

The agreement may define net income, but if it doesn’t I would argue net income to be his gross income minus all deductions.