text: const MODERN_ACTIVITY= 15; 
  const HALF_LIFE_PERIOD= 5730;
  
  module.exports = function dateSample(sampleActivity ) {
    if (!sampleActivity) return false;
    if (typeof(sampleActivity)!='string') return false;
    let sampleActivityNum = parseFloat(sampleActivity);
    if (Number.isNaN(sampleActivityNum) || sampleActivityNum <=0 || sampleActivityNum > MODERN_ACTIVITY) return  false;
    return  Math.ceil(Math.log(MODERN_ACTIVITY/sampleActivityNum)/0.693*HALF_LIFE_PERIOD);
  };
  