Helen purchased a house for $250,000. After providing a 20% down payment, she borrowed the balance from the local savings and loan under a 30-year 4.5% mortgage loan requiring equal monthly installments at the end of each month. Which time value concept would be used to determine the monthly payment?

		Present value of one.
		Future value of one.
		Present value of an ordinary annuity.
		Future value of an ordinary annuity.