function ctl() {

	var a = cart_quantity.a.value; 
	var b = cart_quantity.b.value;

	var tube = Math.ceil((a*b)/12);
	cart_quantity.tube.value = tube;
	cart_quantity.cart_quantity.value = tube;
	var options = document.getElementsByTagName("textarea");
	if (typeof(options) != "undefined")
	{
		var text = "Cut Length: " + a + ", Quantity: " + b;
		if (typeof(options.length) != "undefined")
		{
			if (options.length > 0)
				options[0].value = text;
		}
		else
			options.value = text;
	}

	return false;
}