MongoDB

For each (letter) grade determine the number of students that got that grade

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{ name:Smith, id:159008743, courseId:198:111, semester:Sp2018, examNumber:1, totalQuestions:10, totalCorrect:8, percentage:0.8, grade:B, date_submitted:04-25-2018, time_submitted:19:25:24, room:Hill 363, computerNumber:5, ip:198.253.128.5, questions:[ { number:1, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:false }, { option:B, 1 optionid:384734, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384249, optiontext:Option C, correct:true, answered:true }, { option:D, optionid:3834223, optiontext:Option D, correct:false, answered:false } ] }, { number:2, questionid:34325, questiontext:Question 2, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:false }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, 2 optionid:384729, optiontext:Option D, correct:true, answered:true } ] }, { number:3, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:true, answered:true }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:false, answered:false } ] }, { number:4, questionid:34532, questiontext:Question 1, answers:[ { option:A, 3 optionid:384729, optiontext:Option A, correct:true, answered:true }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:false, answered:false } ] }, { number:5, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:false }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, 4 optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:true, answered:true } ] }, { number:6, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:true, answered:true }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:false, answered:false } ] }, 5 { number:7, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:true }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:true, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:false, answered:false } ] }, { number:8, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:false }, { option:B, 6 optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:false }, { option:D, optionid:384729, optiontext:Option D, correct:true, answered:true } ] }, { number:9, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:false, answered:false }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:true, answered:true }, { option:D, 7 optionid:384729, optiontext:Option D, correct:false, answered:false } ] }, { number:10, questionid:34532, questiontext:Question 1, answers:[ { option:A, optionid:384729, optiontext:Option A, correct:true, answered:false }, { option:B, optionid:384729, optiontext:Option B, correct:false, answered:false }, { option:C, optionid:384729, optiontext:Option C, correct:false, answered:true }, { option:D, optionid:384729, optiontext:Option D, correct:false, answered:false } ] } ] }