class Student extends Person {
    /*	
    *   Class Constructor
    *   
    *   @param firstName - A string denoting the Person's first name.
    *   @param lastName - A string denoting the Person's last name.
    *   @param id - An integer denoting the Person's ID number.
    *   @param scores - An array of integers denoting the Person's test scores.
    */
    // Write your constructor here
    constructor(firstName, lastName, idNumber, testScores){
        super(firstName, lastName, idNumber)
        
        this.testScores = testScores
       
        
    }
    /*	
    *   Method Name: calculate
    *   @return A character denoting the grade.
    */
    // Write your method here
    
    calculate(){
         let avg = 0
         let sum = 0
        for(let i=0; i<this.testScores.length; i++){
             sum += this.testScores[i]
             avg  = sum / this.testScores.length
        }
        
        if(avg>=90 && avg <=100){
                return 'O'
                
            }else if(avg>=80 && avg<90){
                
                return 'E'
            }else if(avg>=70 && avg<80){
                
                return 'A'
            }else if(avg>=55 && avg<70){
                
                 return 'P'
            }else if(avg>=40 && avg<55){
                
                return 'D'
            }else if(avg<40){
                
                return 'T'
            }
        
    }
}