Your client Raj has a $200,000$ mortgage, with monthly payments of $1,200.$ His property tax payments are $275$ per month, based on the home's value of $230,000.$ He has an annual gross income of $75,000,$ and he has $15,000$ invested in mutual funds. Which factors should you use to calculate Raj's total debt service burden?

I. His total assets and his total debts

II$.$ His gross income and his monthly debt payments

III. His gross income and his total debts

IV$.$ His total net worth and his total debts