public static Exam operator +(Exam exam1, Exam exam2)
{
Exam examSum = new Exam(exam1.GetDateTime());
examSum.SetMark(exam1.GetMark() + exam2.GetMark());
return(examSum);
}
public void PassExam(Exam exam)
{
exam.SetMark(10);
_exams.Add(exam);
}