Concate different lists of objects

static void Main()
    {
        try
        {
            List<Student> listStudents = new List<Student>();
            listStudents.Add(new Student("Pesho", "Petrov", 3.00));
            listStudents.Add(new Student("Misho", "Kirov", 4.40));
            listStudents.Add(new Student("Gosho", "Goshev", 6.00));
            listStudents.Add(new Student("Dido", "Mishov", 5.55));
            listStudents.Add(new Student("Valeri", "Nakov", 5.45));
            listStudents.Add(new Student("Petio", "Marinov", 2.00));
            listStudents.Add(new Student("Batman", "Vasilev", 2.10));
            listStudents.Add(new Student("Robin", "Kamenikov", 3.20));
            listStudents.Add(new Student("Ninja", "Zagorkov", 4.44));
            listStudents.Add(new Student("Penka", "Filipova", 2.01));

            List<Worker> listWorkers = new List<Worker>();
            listWorkers.Add(new Worker("Gosho", "Zmeia", 200, 19));
            listWorkers.Add(new Worker("Boiko", "Borisov", 100000, 1));
            listWorkers.Add(new Worker("Ceko", "Popov", 100, 2));
            listWorkers.Add(new Worker("Krisi", "Gosova", 500, 8));
            listWorkers.Add(new Worker("Nina", "Koleva", 300, 9));
            listWorkers.Add(new Worker("Kristina", "Babova", 5, 23));
            listWorkers.Add(new Worker("Tom", "Tomov", 300, 5));
            listWorkers.Add(new Worker("Misho", "Shamara", 400, 7));
            listWorkers.Add(new Worker("Gosho", "Popov", 1000, 10));
            listWorkers.Add(new Worker("Gelio", "Vylev", 250, 3));

            //sort students
            //linq
            var sortedStudents =
            (from stud in listStudents
             orderby stud.Grade
             select stud).ToList();
            //Lambda
            var sortredStudents2 = listStudents.OrderBy(x => x.Grade).ToList();

            //sort workers
            //linq
            var sortedWorkers =
            (from worker in listWorkers
             orderby worker.MoneyPerHour() descending
             select worker).ToList();
            //lambda
            var sortedWorkers2 = listWorkers.OrderByDescending(x => x.MoneyPerHour()).ToList();
            //merge lists
            List<dynamic> mergeList = new List<dynamic>(listStudents.Concat<dynamic>(listWorkers));

            //sort by first name than by last name
            //linq
            var mergeSorted =
            (from man in mergeList
             orderby man.FirstName, man.LastName
             select man).ToList();
            //lambda
            var mergeSorted2 = mergeList.OrderBy(x => x.FirstName).ThenBy(x => x.LastName).ToList();
        }
        catch (ArgumentException err)
        {
            Console.WriteLine(err.Message);
        }
    }

public abstract class Human
{
    private string firstName;
    private string lastName;

    public string FirstName
    {
        get {return this.firstName;}
    }

    public string LastName
    {
        get { return this.lastName; }
    }

    public Human(string firstName, string lastName)
    {
        this.firstName = firstName;
        this.lastName = lastName;
    }
}

public class Student : Human
{
    private double grade;

    public double Grade
    {
        get { return this.grade; }
        private set
        {
            if (value < 2 || value > 6)
            {
                throw new ArgumentException("Invalid grade");
            }
            this.grade = value;
        }
    }


    public Student(string firstName, string lastName, double grade)
        : base(firstName, lastName)
    {
        this.Grade = grade;
    }
}

public class Worker : Human
{
    private decimal weekSalary;

    private int workHoursPerDay;

    public decimal WeekSalary
    {
        get
        {
            return this.weekSalary;
        }
        private set
        {
            if (value <= 0)
            {
                throw new ArgumentException("Week salary must be positive!");
            }
            this.weekSalary = value;
        }
    }

    public int WorkHoursPerDay
    {
        get
        {
            return this.workHoursPerDay;
        }
        private set
        {
            if (value <= 0 || value > 23)
            {
                throw new ArgumentException("Hours must be between 1 and 23 :)");
            }
            this.workHoursPerDay = value;
        }
    }

    public Worker(string firstName, string lastName, decimal weekSalary, int workHoursPerDay)
        : base(firstName, lastName)
    {
        this.WeekSalary = weekSalary;
        this.WorkHoursPerDay = workHoursPerDay;
    }

    public decimal MoneyPerHour()
    {
        return this.weekSalary / this.workHoursPerDay * 5;
    }
}