How to write correctly address Talent Agent and agency?

[librarian]

greetings!
I am attempting to send letter to Estelle Parsons.
I know who her Talent Agent is, and the address to the agency. But, how do I correctly write it on the envelope?

c/o Richard Smith (this is a hypothetical name of the agent.)
Paradigm Agency
360 Park Avenue South
16th Floor
New York, NY 10010
or

Ms. Estelle Parsons
Paradigm Agency
c/o Richard Smith
360 Park Avenue South
16th Floor
New York, NY 10010
or
Ms. Estelle Parsons
c/o Paradigm Agency
360 Park Avenue South
16th Floor
New York, NY 10010
ATTN (Mr. Richard Smith)?

Finally, this:
Ms. Estelle Parsons
c/o Paradigm Agency
360 Park Avenue South
16th Floor
New York, NY 10010

Which way is correct? perhaps, it doesn't matter?
Please help!

[DanaRenoMBA]

Frankly I don't think it makes much of a difference. However, of your four possibles, I believe I would prefer either of the last two. I'm sure my opinion doesn't mean much, but there it is for what it's worth.

Good luck whatever you decide.

[librarian]

thanks!!!!

I will go with the last one.

Frankly I don't think it makes much of a difference. However, of your four possibles, I believe I would prefer either of the last two. I'm sure my opinion doesn't mean much, but there it is for what it's worth.

Good luck whatever you decide.