ingumsky

/*
	You'd better find solutions for those assesments yourself to be sure 
	you understand MongoDB Aggregation Framework properly.
	But if you stuck and need some help and clues to guide you
	feel free to use the commands below as a reference.

	Note that I splitted each and every aggregation stage. 
	Hopefully it will help you to find why your code is not working as you want.
*/