Arithmetic Operators

After the setup below, one command returns a value that no document stores: how much each product's stock is worth.

db.products.drop()
db.products.insertMany([
  { name: "Product A", price: 10, quantity: 100 },
  { name: "Product B", price: 20, quantity: 150 },
  { name: "Product C", price: 15, quantity: 200 },
  { name: "Product D", price: 25, quantity: 50 }
])

db.products.aggregate([
  { $project: { _id: 0, name: 1, stockValue: { $multiply: ["$price", "$quantity"] } } }
])

[
  { name: 'Product A', stockValue: 1000 },