public override string ToString()
{
return(String.Format("First Name : {0}\n Second Name : {1}\n Faculty Number :{2}\n Phone : {3}\n Email : {4}\n Avarage Grade: {5}\n Group : {6}", FirstName, LastName, FacultyNumber, Phone, Email, Marks.Average(), GroupNumber));
}
public void PrintAverageMark()
{
var avg = Marks.Average(a => (int)a);
Console.WriteLine($"Average mark of {Name}: {avg}");
}