code: function multiplyDuration(startDuration, multiplier) {
  
    if(!isFinite(multiplier) || multiplier <= 0) {
      throw new Error('Invalid Multiplier');
    }
  
    var newDuration = {},
        hasTime = false,
        duration = '';
  
    if(startDuration.getSeconds()) {
      newDuration.seconds = Math.round(startDuration.getSeconds()*multiplier);
    }
  
    if(startDuration.getMinutes()) {
      newDuration.minutes = Math.round(startDuration.getMinutes()*multiplier);
    }
  
    if(startDuration.getHours()) {
      newDuration.hours = Math.round(startDuration.getHours()*multiplier);
    }
  
    if(startDuration.getDays()) {
      newDuration.days = Math.round(startDuration.getDays()*multiplier);
    }
  
    if(startDuration.getMonths()) {
      newDuration.months = Math.round(startDuration.getMonths()*multiplier);
    }
  
    if(startDuration.getYears()) {
      newDuration.years = Math.round(startDuration.getYears()*multiplier);
    }
  
    if(newDuration.seconds) {
      hasTime = true;
      duration = newDuration.seconds+'S'+duration;
    }
  
    if(newDuration.minutes) {
      hasTime = true;
      duration = newDuration.minutes+'M'+duration;
    }
  
    if(newDuration.hours) {
      hasTime = true;
      duration = newDuration.hours+'H'+duration;
    }
  
    if(hasTime) {
      duration = 'T'+duration;
    }
  
    if(newDuration.days) {
      duration = newDuration.days+'D'+duration;
    }
  
    if(newDuration.months) {
      duration = newDuration.months+'M'+duration;
    }
  
    if(newDuration.years) {
      duration = newDuration.years+'Y'+duration;
    }
  
    if(!duration) {
      throw new Error('Invalid Duration Multiplier');
    }
  
    return new Duration('P'+duration);
  
  }
docs: Takes in a start duration and a multiplier,
  and returns a new Duration.
  Rounds using Math.round