const saveData = await Student.findOne(
                        {
                            userId,
                            "academicInfo.class":className,
                            "academicInfo.isActive": true,
                            "academicInfo.isDeleted": false,
                            _id,
                            "academicInfo.examDetails": {
                                $elemMatch : {
                                    examType: examType,
                                    examSubject: subject,
                                    totalMarks: totalMark
                                } //query the data from data base
                            }
                        } //query part
                        {
                            $set : {
                                "examDetails.$.result.$.totalMark": totalMark,
                                "examDetails.$.result.$.marks": myMark,
                                "examDetails.$.result.$.rightAnswer": rightAnswer,
                                "examDetails.$.result.$.wrongAnswer": wrongAnswer
                            }
                        }, //update part
                        {} //option
                    )