Can you please explain this?

3) Affordability is obviously one of the biggest factors that the bank will consider when deciding whether or not to give a mortgage. Which two mortgage formulas, as well as percentage cap determines if a bank is willing to lend? a) Gross Debt Service ratio should be more than 32%; Total Debt Service ratio should not be more than 40% b) Gross Debt Service ratio should not be more than 40%; Total Debt Service ratio should be more than 32% c) Gross Debt Service ratio should not be more than 40%; Total Debt Service ratio should not be more than 32% d) Gross Debt Service ratio should not be more than 32%; Total Debt Service ratio should not be more than 40% e) Neither of these formulas are used by the lender if a 20% down payment is provided