function gfr(){
	var creatine= parseFloat(document.gfrd.creatine.value)
	var weight= parseFloat(document.gfrd.weight.value)
	var age= parseFloat(document.gfrd.age.value)
	var num= document.gfrd.crea.selectedIndex
	var num2= document.gfrd.bd.selectedIndex
	
	if (num==0){
		creatine= creatine*11.31 }
	else if (num==1){
		creatine= creatine*0.0113 }
	else {}
	
	if (num2==0){}
	else {
		weight= weight/2.2 }	
	
	if 	(document.gfrd.sex[0].checked){
		document.gfrd.answer.value= parseFloat(((140-age)*(weight))/(72*creatine))
		}
	else {
		document.gfrd.answer.value= parseFloat([((140-age)*(weight))/(72*creatine)]*.85)
		}
}