code: private function getFallDue($prefix)
      {
          return $this
              ->getFallDueQueryBuilder($prefix)
              ->select('SUM(' . $this->getAlias() . '.' . $prefix . 'Total)')
              ->getQuery()
              ->getSingleScalarResult();
      }
docs: Returns the fall due total.
  
  @param string $prefix
  
  @return float