static void Main(string[] args)
{
var aPerson = new Person
{
FirstName = "Alix",
LastName = "Hill"
};
aPerson.SayHello();
var aStudent = new Student
{
FirstName = "Bill",
LastName = "Wang"
};
aStudent.SetAge(21);
aStudent.SayHello();
aStudent.ShowAge();
var aTeacher = new Teacher
{
FirstName = "Mia",
LastName = "Lynn"
};
aTeacher.SetAge(31);
aTeacher.SayHello();
Console.ReadLine();
}