function showpay() {
	if ((document.calc.loan.value == null || document.calc.loan.value.length == 0) ||
	(document.calc.months.value == null || document.calc.months.value.length == 0) ||
	(document.calc.rate.value == null || document.calc.rate.value.length == 0)) { document.calc.pay.value = "Incomplete data"; }
	else {
		var princ = document.calc.loan.value;
		var down = document.calc.down.value;
		var term  = document.calc.months.value;
		var intr   = document.calc.rate.value / 1200;
		document.calc.pay.value = (princ - down) * intr / (1 - (Math.pow(1/(1 + intr), term)));
		} // payment = (principle - down) * monthly interest/(1 - (1/(1+MonthlyInterest)*Months))
	}