function calculate() {
	var NO = '';
	var PA = '';
	var IT = '';
	var PR = '';
	var BA = '';
	var n = 0;
	
	var I = parseFloat(document.forms[0].I.value);
	var L = parseInt(document.forms[0].L.value);
	var P = parseInt(document.forms[0].P.value);
	
	if (isNaN(I)) {
		alert("Please enter an interest rate!");
		return;
	}
	
	if (isNaN(L)) {
		alert("Please enter a loan length in months!");
		return;
	}
	
	if (isNaN(P)) {
		alert("Please enter a loan amount!");
		return;
	}
	
	var J = (I/(12*100));									//monthly interest in decimal form
	var N = L;												//number of months over which loan is amortized
	var M = round(P * ( J / (1 - Math.pow(1 + J,-N))),2)	//monthly payment
	document.forms[0].MP.value = '$' + M;
		
}

function round(number,X) {
	X = (!X ? 2 : X);
	return Math.round(number*Math.pow(10,X))/Math.pow(10,X);
}

function formatCurrency(num) {
	num = num.toString().replace(/\$|\,/g,'');
	
	if(isNaN(num)) num = "0";
	
	sign = (num == (num = Math.abs(num)));
	num = Math.floor(num*100+0.50000000001);
	cents = num%100;
	num = Math.floor(num/100).toString();
	
	if(cents<10) cents = "0" + cents;
	
	for (var i = 0; i < Math.floor((num.length-(1+i))/3); i++)
		num = num.substring(0,num.length-(4*i+3))+','+
	
	num.substring(num.length-(4*i+3));
	return (((sign)?'':'-') + '$' + num + '.' + cents);
}