Answer:
Computer
Explanation:
A common noun is the type of noun that denotes the names of non-specific things such as people, animals, etc.
From the example given, the common noun there is "computer" because it does not mention a specific thing like the type of computer.
The tone is the way the author expresses his attitude through their writing.
The tone can change, or stay the same way throughout the literary work.
Tone is expressed by your point of view, your diction, etc.
Hope this helped!