Why am I getting the following? 'Your setter method is returning the wrong value for the major property.'

class Student {
    constructor(gpa, credits){
        this.gpa = gpa;
        this.credits = credits;
    }

    stringGPA() {
        return this.gpa.toString();
    }

    set major(major) {
      this._major = major;

        if(this.level == 'Junior' || this.level == 'Senior') {
        return major;
      } else if(this.level == 'Freshman' ||  this.level == 'Sophmore') {
        return major = 'None';
      }
    }

    get level() {
        if (this.credits > 90 ) {
            return 'Senior';
        } else if (this.credits > 60) {
            return 'Junior';
        } else if (this.credits > 30) {
            return 'Sophomore';
        } else {
            return 'Freshman';
        }
    }
}

var student = new Student(3.9, 60);