function calculate()
{  
  var amount = null;
  var price = 5;
  var heightElement = document.calculator.height.value;
  var widthElement = document.calculator.width.value;
  var sqfeet = heightElement * widthElement;
  var amount = sqfeet * price;
  var priceField = document.getElementById("price");
	priceField.setAttribute("value", "$ " + amount);
  return true;
}