Javascript/潔癖症診断

var a = 0;
var b = 0;
var c;
function shindan(){
  var ten = new Array(0,3,6,9,12);
  for (i=0; i<5; i++){
    if(document.radioBtn.elements[ten[i]].checked)
      a++;
  }
  a = a * 20;
  
  var five = [1, 4, 7, 10, 13];
  for(j=0; j<5; j++){
  	if(document.radioBtn.elements[five[j]].checked)
  	  b++;
  }
  b = b * 10;
  c = a + b;

  if(c >= 75){
  	alert(c + "点！！　あなたは潔癖症！！");
  } else if(c < 75 && c >= 30){
  	alert(c + "点！！　あなたはやや潔癖症！");
  } else {
  	alert(c + "点！！　あなたは潔癖症ではない！");
  }
  a = 0;
  b = 0;
}