Use either a method find$()$ or a method aggregate$()$ available in MongoDB to write the

implementations of the following queries. Implementation of each query is worth $2$ marks.

$(1)$ Find the title, authors, publisher, year and price of all books which are

published before $2015.$

$(2)$ Find the title, publisher, year and price of all books which contain a word C$++$

in the description.

$(3)$ Find the title, publisher, year and price of all books which have at least $2$

keywords