How to sum from average result

hi guy’s i need some help for deadline task.
this is sample of my document and query :point_down:

my query always give 0 result
the question is how to get a final score from sum average
i wish the result become like this

[
  {
    "_id": "NILAI HARIAN",
    "average": 77.85714285714286,
    "many": 7,
    "sum": 545
  },
  {
    "_id": "PENILAIAAN TENGAH SEMESTER",
    "average": 80,
    "many": 1,
    "sum": 80
  },
  {
    "_id": "PENILAIAAN AKHIR SEMESTER",
    "average": 73,
    "many": 1,
    "sum": 73,
    "final_score": 0,
  }
]

A field that is created in a stage is only available in the next stage. In your $group, the field average: cannot be used to compute final_score:.

average: {
        $avg: "$datas.report.scores.value",
        
      },
      final_score: {
        $sum: "$average"
      }

and how to make return became like this

[
  {
    "_id": "PENILAIAAN AKHIR SEMESTER",
    "average": 73,
    "many": 1,
    "sum": 73
  },
  {
    "_id": "NILAI HARIAN",
    "average": 77.85714285714286,
    "many": 7,
    "sum": 545
  },
  {
    "_id": "PENILAIAAN TENGAH SEMESTER",
    "average": 80,
    "many": 1,
    "sum": 80
  },
"final_score":230
]

final score got from sum of average ?

Share what you have tried and explained how it failed to provide the desired result.

This would help us save time by not investigation in a direction that you already know does not work.