Database
[{title:"Vivo X50",category:"mobile",amount:35000},{title:"Samsung M32",category:"mobile",amount:18000},{title:"Lenovo 15E253",category:"laptop",amount:85000},{title:"Dell XPS 15R",category:"laptop",amount:115000}]
Query
db.collection.aggregate([{$group:{_id:"$category",qty:{$sum:1},totalAmount:{$sum:"$amount"}}},{$project:{_id:0,category:"$_id",qty:"$qty",totalAmount:"$totalAmount"}}])