in c#

class Student : Person{ private int[] testScores;

public Student(string firstName,string lastName,int id,int[] scores):
base(firstName,lastName,id)
{
            testScores=scores;
}

public char Calculate()
{
   int avg= testScores.Sum() /testScores.Count();

    switch(avg)
    {
        case int n when n>=90 &&  n<=100:
            return 'O';
            break;
        case int n when n>=80 && n<90:
            return 'E';
            break;
        case int n when n>=70 && n<80:
            return 'A';
            break;
        case int n when n>=55 && n<70:  
            return 'P';
            break; 
        case int n when n>=40 && n<55:  
            return 'D';
            break;
         case int n when  n<40:  
            return 'T';
            break; 
        default :
        return ' ';
        }

}

}