with_obj.cs

using System.Collections.Generic;

namespace journey_01
{
    public class Person01
    {
        public int ID;
        public string Name;
        public List<string> Classes;

        public Person01()
        {
            Classes = new List<string>();
        }

        public bool IsInClass(string cls)
        {
            return Classes.Contains(cls);
        }
    }

    public class Teacher01 : Person01
    {
        public short Parking;
    }

    public class Student01 : Person01
    {
        public float GPA;
    }

}