function show_image(num)
{
	if (document.images)
  	{
   		imgOn = eval("image_" + num + ".src");
  		 document.getElementById('main_image').src = imgOn;
	}
}

String.prototype.trim = function() {
	a = this.replace(/^\s+/, '');
	return a.replace(/\s+$/, '');
};

function showpay() 
{
	var ask_price 	= document.getElementById("ask_price").value.replace(/[^0-9.]/g, "").trim();
	var interest   	= document.getElementById("interest_rate").value.trim() / 1200;
	var term  		= document.getElementById("length").value.replace(/[^0-9]/g, "").trim();
	
	if ((ask_price == null || ask_price.length == 0) || (interest == null || interest == 0 || interest.length == 0) || (term == null || term.length == 0))
 	{ 
 		document.getElementById("payment").innerHTML = "Incomplete data";
 	}
	else
	{
 		document.getElementById("payment").innerHTML = "$" + (ask_price * interest / (1 - (Math.pow(1/(1 + interest), (term * 12))))).toFixed(2);
 	}
	// payment = principle * monthly interest/(1 - (1/(1+MonthlyInterest)*Months))
}

function checkIt(evt) 
{
	evt = (evt) ? evt : window.event;
    var charCode = (evt.which) ? evt.which : evt.keyCode;
	
    if (charCode > 31 && (charCode < 48 || charCode > 57)) {
        status = "This field accepts numbers only.";
        return false;
    }
    status = "";
    return true;
}