def required_parent_amount_rule(model, pr, pa):
    """
    In order for a parent resource to be allocated to a parent activity, a certain amount of parent budget is required.
    A parent activity is selected if and only if the provided amount is sufficient.

    :param ConcreteModel model:
    :param int pr: parent resource
    :param int pa: parent activity
    :return: boolean indicating whether the needed amount is allocated from pr to pa
    """
    return model.PARENT_AMT[pr, pa] == model.req_parent_amt[pr, pa] * model.PARENT_ALLOCATED[pr, pa]