Can someone help me with this C Sharp Program?

[mistnicgy]

I can't seem to get this to produce a letter grade. I am just learning this and just can't seem to get it. Any help would be appreciated.


using System;

namespace LetterGrade
{
class Program
{
static void Main()
{
double examScore1,
examScore2,
examScore3,
examScore4,
examScore5,
average;

char letter;

DisplayInstructions();

examScore1 = GetScore("First");
examScore2 = GetScore("Second");
examScore3 = GetScore("Third");
examScore4 = GetScore("Fourth");
examScore5 = GetScore("Fifth");
average = GetAverage(examScore1, examScore2, examScore3, examScore4, examScore5);

letter = DetermineGrade();

DisplayResult(letter);




}

public static void DisplayInstructions()
{
Console.WriteLine("This program will ask you to enter five test scores.");
Console.WriteLine("It will then give you a letter grade based on the average.");
Console.WriteLine();
}

public static double GetScore(string value)
{
string inputValue;
double score;

Console.Write("Please enter the {0} score : ", value);
inputValue = Console.ReadLine();
score = double.Parse(inputValue);
return score;
}

public static double GetAverage(double s1, double s2, double s3, double s4, double s5)
{
double average;

average = (s1 + s2 + s3 + s4 + s5) / 5;
return average;
}


public static char DetermineGrade()
{
char letter;


if ( average > 89)
letter = 'A';
else if (average > 79)
letter = 'B';
else if (average > 69)
letter = 'C';
else if (average > 59)
letter = 'D';
else
letter = 'F';
}

public static void DisplayResult(char letter)
{
Console.WriteLine();
Console.WriteLine(" The numeric grade is : " + letter);
Console.ReadLine();




}
}
}