@staticmethod
def _classification_function_four(salary, commission, age, elevel, car,
    zipcode, hvalue, hyears, loan):
    """ classification_function_four

        Parameters
        ----------
        salary: float
            Numeric feature: Salary.

        commission: float
            Numeric feature: Commission.

        age: int
            Numeric feature: Age.

        elevel: int
            Categorical feature: Education level.

        car: int
            Categorical feature: Car maker.

        zipcode; int
            Categorical feature: Zipcode.

        hvalue: flaot
            Numeric feature: Value of the house.

        hyears: float
            Numeric feature: Years house owned.

        loan: float
            Numeric feature: Total amount of loan.

        Returns
        -------
        int
            Returns the sample class label, either 0 or 1.

        """
    if age < 40:
        if 50000 <= salary and salary <= 100000:
            return 0 if 100000 <= loan and loan <= 300000 else 1
        else:
            return 0 if 200000 <= salary and salary <= 400000 else 1
    elif age < 60:
        if 75000 <= salary and salary <= 125000:
            return 0 if 200000 <= salary and loan <= 400000 else 1
        else:
            return 0 if 300000 <= salary and salary <= 500000 else 1
    elif 25000 <= salary and salary <= 75000:
        return 0 if 300000 <= loan and loan <= 500000 else 1
    else:
        return 0 if 75000 <= loan and loan <= 300000 else 1
