public function store(Quiz $quiz, Request $request)
 {
     $student_id = Auth::user()->student()->first()->id;
     if (Score::whereQuizIdAndStudentId($quiz->id, $student_id)) {
         return "e";
     }
     $points = 0;
     foreach ($request->all() as $r) {
         $ca = CorrectAnswer::whereQuestionId($r['question_id'])->first()->option_id;
         if ($ca == $r['option_id']) {
             $points++;
         }
         if (!Answer::whereStudentIdAndQuestionId($student_id, $r['question_id'])->first()) {
             Answer::create(['student_id' => $student_id, 'question_id' => $r['question_id'], 'option_id' => $r['option_id']]);
         }
     }
     $score = Score::create(['score' => $points, 'time' => time() - strtotime($quiz->date_time), 'quiz_id' => $quiz->id, 'student_id' => $student_id]);
     DB::table('quiz_student')->insert(['student_id' => $student_id, 'quiz_id' => $quiz->id]);
     return $score;
 }