class Tank:

    def __init__(self, name, total, dead, act_in=None):
        self._name = name
        self._total = total
        self._dead = dead
        self._act_in = act_in

    def _read_act_in(self):
        raise NotImplementedError

    @property
    def name(self):
        return self._name

    @property
    def total_volume(self):
        return self._total

    @property
    def actual_volume(self):
        return self._act_in

    @property
    def empty_volume(self):
        return self._total - self._act_in

    @property
    def dead_volume(self):
        return self._dead

    @property
    def refuel_volume(self):
        return self._total - self._act_in - self._dead