text: 
  const MODERN_ACTIVITY= 15; 
  const HALF_LIFE_PERIOD= 5730;
  
  module.exports = function dateSample(sample) {
  
    //check if input param:
    if (typeof sample !== "string" || //isn't a string
        /[A-Za-z]/.test(sample) || //has letters
        sample <= 0 || sample > MODERN_ACTIVITY) //is inadequate
    return false;
  
    let rate = Math.LN2.toFixed(3) / HALF_LIFE_PERIOD;
    let years = Math.log(MODERN_ACTIVITY / parseFloat(sample)) / rate;
    return Math.ceil(years);
    
  };