The plural noun 'contestants' is a common noun; a general word for two or more people engaged in a competition; a word for any contestants of any kind.A proper noun is the name or title of a specific person, place, or thing.
All contestants dress as gorillas
Teachers I would presume.
"Park Avenue" is a proper noun, because it is a place. Proper nouns like this should always be capitalized.
proper
Common
common and proper
common
It is a proper noun, because it is the name of a specific thing.
common
it's a common noun. a proper noun would be Spider-Man.
Pencil proper or common noun