function compute(ntc) {
	  var d = document.getElementById("ntc");
	  var curNS = d.terms[0].value;
	  var aveNS = d.terms[1].value;
	  var curNSD = d.terms[2].value;
	  var aveNSD = d.terms[3].value;
	  var curH = d.terms[4].value;
	  var aveH = d.terms[5].value;
	  var curHD = d.terms[6].value;
	  var aveHD = d.terms[7].value;
	  var curIH = d.terms[8].value;
	  var aveIH = d.terms[9].value;
	  var curIHD = d.terms[10].value;
	  var aveIHD = d.terms[11].value;
	  var tmp_result = 100./6*((curNS/aveNS)+(curNSD/aveNSD)+(curH/aveH)+(curHD/aveHD)+(curIH/aveIH)+(curIHD/aveIHD));
          var fix_result = Round(tmp_result,1);
	  d.result.value = fix_result;
          return fix_result
	}

        function Round(num,precision) { 
          //convert num to string 
          num = "" + num;
          precision = parseInt(precision); 

          //convert desired result to integer
          //unwanted digits will be after the decimal point
          var fullNum = "" + Math.round(num* Math.pow(10, precision)); 

          //find where decimal point should go 
          var decPoint = fullNum.length - precision; 

          if (decPoint != 0) { 
            //concatenate left and right part of the decimal together 
            result = fullNum.substring(0, decPoint); 
            result += "."; 
            result += fullNum.substring(decPoint, fullNum.length); 
          } else { 
            result = fullNum; 
          } 
          return result; 
        } 
	
	function loadyear(ntc) {
	
	  //define arrays of values for each year (NS, NSD, H, HD, IH, IHD)
          var custom = new Array("", "", "", "", "", "");
	  var _2008_ = new Array(16, 88.25, 8, 30.50, 5, 7.50);
	  var _2007_ = new Array(15, 37.75, 6, 12.25, 2, 6.00);
	  var _2006_ = new Array(10, 52.75, 5, 21.25, 2, 2.00);
	  var _2005_ = new Array(27, 128.75, 15, 49.75, 7, 17.75);
	  var _2004_ = new Array(14,  90.00,  9, 45.50, 6, 22.25);
	  var _2003_ = new Array(16,  79.25,  7, 32.75, 3, 16.75);
	  var _2002_ = new Array(12,  53.50,  4, 10.75, 2,  3.00);
	  var _2001_ = new Array(15,  64.25,  9, 25.50, 4,  4.25);
	  var _2000_ = new Array(14,  67.00,  8, 32.75, 3,  5.00);
	  var _1999_ = new Array(12,  78.50,  8, 41.00, 5, 14.25);
          var _1998_ = new Array(14,  88.00, 10, 48.50, 3,  9.50);
          var _1997_ = new Array( 7,  28.75,  3,  9.50, 1,  2.25);
          var _1996_ = new Array(13,  79.00,  9, 45.00, 6, 13.00);
          var _1995_ = new Array(19, 121.25, 11, 61.75, 5, 11.50);
          var _1994_ = new Array( 7,  27.75,  3,  7.25, 0,  0.00);
	  
	  var d = document.getElementById("ntc");
          for (i=0;i<d.year.length;++i) {
            if (d.year[i].checked) { Year = d.year[i].value; }
          }

          //fill in the table with values for the selected year
          if (Year == "custom") { YearArray = custom; }
	  if (Year == "2008") { YearArray = _2008_; }
	  if (Year == "2007") { YearArray = _2007_; }
          if (Year == "2006") { YearArray = _2006_; }	  
          if (Year == "2005") { YearArray = _2005_; }	  
          if (Year == "2004") { YearArray = _2004_; }	  
          if (Year == "2003") { YearArray = _2003_; }
          if (Year == "2002") { YearArray = _2002_; }
          if (Year == "2001") { YearArray = _2001_; }
          if (Year == "2000") { YearArray = _2000_; }
          if (Year == "1999") { YearArray = _1999_; }
          if (Year == "1998") { YearArray = _1998_; }
          if (Year == "1997") { YearArray = _1997_; }
          if (Year == "1996") { YearArray = _1996_; }
          if (Year == "1995") { YearArray = _1995_; }
          if (Year == "1994") { YearArray = _1994_; }
          //average values are already loaded into odd-numbered indices
          for (j=0;j<6;++j) { d.terms[j*2].value = YearArray[j]; }
	  //compute the NTC for the selected year using pre-defined values
          return compute(d.terms);
	}