What is the difference between network administrators and system administrators?

Network administrators are responsible for all of the individual machines in a network; systems administrators are responsible for the machines' connections and interactions with each other

Network administrators are responsible for the machines' connections and interactions with each other; Systems administrators are responsible for all of the individual machines in a network

Network administrators are responsible for the Network Operating System $($NOS$)$; systems administrators are responsible for all physical infrastructure

Network administrators are responsible for all physical infrastructure; systems administrators are responsible for the Network Operating System $($NOS$)$