function calc()
{
var width=parseInt(document.form1.T1.value);
var length=parseInt(document.form1.T2.value);
var irList = document.getElementById('T3');
var ir=parseInt(irList.options[irList.selectedIndex].text);
document.getElementById("lbl").innerHTML =(Math.sqrt((ir+width)*(ir+width)+(length/2)*(length/2))-(ir-2)).toFixed(2);

}