Implementation of 4x1 multiplexer and 1x4 demultiplexer using logic gates.

How many NOT gates are required for the construction of a 4-to-1 multiplexer?
In 1-to-4 demultiplexer, how many select lines are required?
How many select lines are required for a 1-to-8 demultiplexer?
Which IC is used for the implementation of 1-to-16 DEMUX?
The enable input is also known as ___________