Что не так с этим java-кодом? Подсказка : что-то связанное с наследованием

Whats wrong with this java code? HINT: related to inheritanc

<pre>import java.util.*;
import java.lang.String;

class Person {
	protected String firstName;
	protected String lastName;
	protected int idNumber;
	
	// Constructor
	Person(String firstName, String lastName, int identification){
		this.firstName = firstName;
		this.lastName = lastName;
		this.idNumber = identification;
	}
	
	// Print person data
	public void printPerson(){
		 System.out.println(
				"Name: " + lastName + ", " + firstName 
			+ 	"\nID: " + idNumber); 
	}
	 
}

class Student extends Person{
	private int[] testScores;

    
	/*	
    *   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
    
    Student(String firstName, String lastName, int id, int[] testScores)
    {
        this.firstName = firstName;
	this.lastName = lastName;
	this.idNumber = id;
        this.testScores = testScores;
    }
    /*	
    *   Method Name: calculate
    *   @return A character denoting the grade.
    */
    // Write your method here
    public char calculate()
    {
        int totalMarks = 0;
        char grade;
        for(int i = 0; i<testScores.length;i++)
        {
            totalMarks = totalMarks + testScores[i];
        }
        if(totalMarks >=90 ){
            grade = 'O';
    
        }else if(totalMarks >=80 && totalMarks < 90)
        {
            grade = 'E';
        }else if(totalMarks >=70 && totalMarks < 80)
        {
            grade = 'A';
        }else if(totalMarks >=55 && totalMarks < 70)
        {
            grade = 'p';
        }else if(totalMarks >=40 && totalMarks < 55)
        {
            grade = 'D';
        }else 
        {
            grade = 'T';
        }
        return grade;
    }
}

class Solution {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		String firstName = scan.next();
		String lastName = scan.next();
		int id = scan.nextInt();
		int numScores = scan.nextInt();
		int[] testScores = new int[numScores];
		for(int i = 0; i < numScores; i++){
			testScores[i] = scan.nextInt();
		}
		scan.close();
		
		Student s = new Student(firstName, lastName, id, testScores);
		s.printPerson();
		System.out.println("Grade: " + s.calculate());
	}
}