text: const MODERN_ACTIVITY = 15
  const HALF_LIFE_PERIOD = 5730
  const k = 0.693 / HALF_LIFE_PERIOD
  
  module.exports = function dateSample(final_activity) {
    if(typeof(final_activity) != 'string') return false
    final_activity = parseFloat(final_activity)
    if(isNaN(final_activity) || final_activity <= 0 || final_activity > MODERN_ACTIVITY) return false
  
    const N0dN = MODERN_ACTIVITY / final_activity
  
    return Math.ceil( Math.log(N0dN) / k )
  };
  