Crosstab groups, multiple columns - MongoDB question

I am trying to make a cross tab that looks similar to this:

My data is coming out of MongoDB and the points possible, points achieved, unanswered and percent score are being returned within a sub-document like this:

   "sample" : "1",
                    "score" : {
                       "pointsPossible" : NumberLong(68),
                        "pointsAchieved" : 39.0,
                        "unanswered" : NumberLong(0),
                        "pctScore" : 0.5672
                   }

How do I treat pointsPossible, pointsAchieved, unanswered and pct score as dynamic columns to add under each assessment in my cross-tab?

Is this possible, or does the document structure in Mongo need to be changed to make this work?