MongoDB - Writing in table by calculating values from object and another table

Assume there is a collection names productRecord which stores the documents in following way:

{
  _id : //id,
  productName : // product name,
  productPrice : //price of product,
  productQuantity: //quantity of product in stock
}

and I have recieved sale object(recieved after sale is made) in format:

var sale = {
  memberId : //id
  products : [
     {productId : //id1, qty : //quantity sold},
     {productId : //id2, qty : //quantity sold},
     {productId : //id3, qty : //quantity sold}
   ]
}

The memberId relates to another table that stores members' detail. I need enter the value in another table named 'saleRecords' in format:

{
  id: //id,
  memberId: //members' id
  products : [
     {productId : //id1, qty : //quantity sold},
     {productId : //id2, qty : //quantity sold},
     {productId : //id3, qty : //quantity sold}
   ] // same as above ,
   totalsaleprice: //this will be sale.qty * productRecord.productPrice (both related using productId)
}

The saesRecord can have multiple entry of same memberId relating to different purchases(sales) he's made. But the price is in the 'productRecord' collection, the qty in the sales record objects and the value needs to be entered in 'salesRecords' connection. How do I write a query for this?