function floor(number)
  {
  return Math.floor( number * Math.pow(10,2)) / Math.pow(10,2);
  }
  
function dosum()
  {
  
  var mi = document.calc.IR.value / 1200;
  var base = 1;
  var mbase = 1 + mi;
  
  for (i=0; i<document.calc.YR.value * 12; i++)
      {
      base = base * mbase
      }
      
  document.calc.PI.value = floor(document.calc.LA.value * mi / (1 - (1/base)))
  document.calc.MT.value = floor(document.calc.AT.value / 12)
  document.calc.MI.value = floor(document.calc.AI.value / 12)
  document.calc.MP.value = floor(document.calc.LA.value * mi / (1 - (1/base))) + (document.calc.AT.value / 12)
  + (document.calc.AI.value / 12);
  }