a.py

class Rectangle:
    def __init__(self,length,width):
        self.length = length
        self.width = width
    
    def area(self):
        return self.length * self.width

    def peremeter(self):
        return (self.length + self.width) * 2

class Square(Rectangle):
    def __init__(self,length):
        super().__init__(length,length)


class Cube(Square):
    def surface_area(self):
        face_area = super().area()
        return face_area * 6
    
    def volume(self):
        face_area = super().area()
        return face_area * self.length