handwritten???

I would not consider it a good idea.

Why would you want to when you obviously have computer access to produce a typed letter?

Not for something like this.

I'm with the others... no hand-written letters.

Your signature can be handwritten. Type the rest of it.
Good question though. How would you know until you ask?

It wasn't a dumb question, especially considering you are going to answer a specific question from the agent. However, a typed letter will look more professional and be better. Later on, as you and the agent get to know each other a short hand-written answer will probably be fine. Congratulations on getting an agent to request the proposal.

Always hand write your thank you notes. You do send thank you notes, right?