//discount percentage
var discount = 0;

function calculate() {
		variant = document.calculator.variant.value;
		rob = 0;
		area = document.calculator.area.value;

		if (document.calculator.robbery.checked && document.calculator.variant.value && document.calculator.area.value) {
			rob = parseInt(document.calculator.robsum.value);
		}

		priceval = (variant*area)*(100 - discount)/100+rob;

		if (priceval>0) {
			if (priceval.toFixed) {
				document.calculator.price.value = priceval.toFixed(2);
			} else {
				document.calculator.price.value = priceval;
			}
		} else {
			document.calculator.price.value = '';
		}

}

function display_sum(chkbox) {
	if (document.all) {
		if (chkbox.checked) {
			document.all["sum"].style.display = 'inline';
		} else {
			document.all["sum"].style.display = 'none';
		}
	} else {
		if (chkbox.checked) {
			document.getElementById("sum").style.display = 'inline';
		} else {
			document.getElementById("sum").style.display = 'none';
		}
	}
}