Why does char in looping always evaluate to - ( DONE )

I'm newbie in Java. So question might sound simple, but I'm stuck and can not figure out why this grade always return to '-'?

file:Student.java

{
    private String studID;
    private double score;

    public String getStudID()
    {
        return studID;
    }

    public void setStudID(String newID)
    {
        studID = newID;
    }

    public double getScore()
    {
        return score;
    }

    public void setScore(double newScore)
    {
        score  = newScore;
    }

    public char determineGrade()   
    {
        if(score>= 100 && score <=80)
        {
            return 'A';
        }
        else if( score >=79 && score <= 70)
        {
            return 'B';
        }
        
        else if(score>=69 && score<= 60)
        {
            return 'C';
        }
        
        else if(score>=59 &&score<= 50)
        {
            return 'D';
        }
        
        else if(score>=49 && score<=0)
        {
            return 'E';
        }
        else
        {
            return '-';     
        }
    }
    public String toString()
    {
        return "\nStudent ID :" + studID + "\nScore : " +  score +  "\nYour Grade is  " + determineGrade(score);
    }

}```


file : Client.java

  import java.util.Scanner;

  public class Client {
    
public static void main(String[] args)
{
   Scanner myObj = new Scanner(System.in);
    Student ob1 = new Student();
    System.out.print("Enter Your Student ID : ");
    ob1.setStudID(myObj.next());
    System.out.print("Enter Your Score : ");
    ob1.setScore(myObj.nextDouble());
    System.out.println(ob1.toString());        
}

}```

output

Student ID : AD11111
Score : 90
Your Grade is -

Why am I getting Output '-' for grade even though i set the mark between 0-100.How should i use mutator when i use if.....else but when i use accessors method it working well