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