[{_id:1,firstName:"John",lastName:"King",gender:"male",email:"john.king@abc.com",salary:5000,department:{"name":"HR"}},{_id:2,firstName:"Sachin",lastName:"T",gender:"male",email:"sachin.t@abc.com",salary:8000,department:{"name":"Finance"}},{_id:3,firstName:"James",lastName:"Bond",gender:"male",email:"jamesb@abc.com",salary:7500,department:{"name":"Marketing"}},{_id:4,firstName:"Rosy",lastName:"Brown",gender:"female",email:"rosyb@abc.com",salary:5000,department:{"name":"HR"}},{_id:5,firstName:"Kapil",lastName:"D",gender:"male",email:"kapil.d@abc.com",salary:4500,department:{"name":"Finance"}},{_id:6,firstName:"Amitabh",lastName:"B",gender:"male",email:"amitabh.b@abc.com",salary:7000,department:{"name":"Marketing"}}]

db.collection.aggregate([{$match:{gender:"male"}},{$sort:{salary:1}},{$group:{_id:{deptName:"$department.name"},totalEmployees:{$sum:1},leastSalary:{$first:"$firstName"}}},{$sort:{deptName:1}}])