var Student = function (name, age, major) {
    Person.call(this, name, age);
    this.major = major;
};

Student.prototype = new Person();
Student.prototype.getMajor = function() {
return this.major;
};
Student.prototype.toString = function(){
return this.name + " - " + this.age + " - " + this.major;
};

var Instructor = function (name, age, title) {
Person.call(this, name, age);
this.title = title;
};

Instructor.prototype = new Person();

Instructor.prototype.getTitle = function () {
return this.title
};
Instructor.prototype.toString = function () {
return this.title + " " + this.name + " - " + this.age;
};

Course = function (courseName, instructor) {
this.students = []
this.instructor = instructor
};
Course.getRoster = function() {
return this.students
};

Course.getCourseName = function() {
return this.courseName
};

Course.prototype.getAverageAge = function() {
for (var i = 0; i < student.length ; i++) {
ages = ages + student[i].age;
};
return ages/student.length;