Справка по ошибке java display не может найти символ

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Я получаю ошибку:

Student.java:96: ошибка: не удается найти символ
С1.дисплей();
^
символ: переменная s1
местонахождение: студент класса
1 ошибка

Что я уже пробовал:

public class Student extends Person {
	
	private int studentId; 
	private String major; 
	private double GPA; 
	
	public Student() { 
		// TODO Auto-generated constructor stub 
		super(); 
		this.studentId = 0; 
		this.major = "";
		GPA = 0.0; 
	}
	
	/**
		@param firstName 
		@param lastName 
		@param address 
		@param email 
		@param studentId 
		@param major 
		@param gPA 
	*/
	
	public Student(int studentId, String firstName, String lastName, 
	String Address, String email, String major, double gPA) {
		super(firstName, lastName, Address, email); 
		this.studentId = studentId; 
		this.major = major;
		GPA = gPA; 
	}
	
	/**
		*@return the studentId
	*/
	public int getStudentId() { 
		return studentId;
	}
	
	/**
		*@return the major
	*/
	public String getMajor() {
		return major;
	}
	
	/**
		*@return the gPA
	*/
	public double getGPA() {
		return GPA;
	}
	
	/**
		*@param studentId
		*the studentId to set
	*/
	public void setStudentId(int studentId) {
		this.studentId = studentId;
	}
	
	/**
		*@param major
		*the major to set
	*/
	public void setMajor(String major) { 
		this.major = major; 
	}
	
	/**
		*@param gPA
		*the gPA to set
	*/
	public void setGPA(double gPA) { 
		GPA = gPA; 
	}
	
	public void display() {
		// print the student details 
		System.out.println("STUDENT ID : " + this.studentId); 
		System.out.println("MAJOR: " + this.major); 
		System.out.println("GPA : " + this.GPA); 
		super.display(); 
	}
	
	public static void main(String[] args) { 
		Student sl; 
		sl = new Student(900077661, "Bill", "Clinton", "70 Bowman St. South Windsor, CT 06074", 
		"bc@msn.com", "CS", 3.5); 
		s1.display();
	}
}

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