/**
  * @param Drinking $drinking
  * @return int
  */
 public static function getDailyMaxUnits(Drinking $drinking)
 {
     $units = array();
     $instance = new self();
     $units[] = $instance->calculateDrinkingUnits($drinking, 'week');
     $units[] = $instance->calculateDrinkingUnits($drinking, 'weekend');
     $units[] = $instance->calculateDrinkingUnits($drinking, 'occasional');
     return (int) round(max($units));
 }