public function __construct($m = 1, $advance = false, $delta = 0, $term = 1, $principal = 0)
 {
     parent::__construct($m, $advance, $delta, $term);
     $this->set_principal($principal);
 }
 public function __construct($m = 1, $advance = false, $delta = 0, $term = 1, $increasing = true)
 {
     parent::__construct($m, $advance, $delta, $term);
     $this->set_increasing($increasing);
 }
 public function __construct($m = 1, $advance = false, $delta = 0, $term = 1, $escalation_frequency = 1, $escalation_delta = 0)
 {
     parent::__construct($m, $advance, $delta, $term);
     $this->set_escalation_delta($escalation_delta);
     $this->set_escalation_frequency($escalation_frequency);
 }