def pmt_pv(i, n, PV, PV0=0):
    """
    Calculates the installment of a present Value.

    :param i:   Interest rate
    :param n:   Number of periods
    :param PV:  Present Value
    :param PV0: Payment at t=0/ Down Payment
    :return:
    """
    return i / (1 - 1 / (1 + i) ** n) * (PV - PV0)