I'm looking forward to receiving your favorable answer.

I'll answer you tomorrow.

You shall have my answer tomorrow.

I hope you will answer soon.

Please reply by return.

Please give us your answer as soon as possible.

Would you please answer as soon as you can?

Regrettably, we have not received your reply.

I'm looking forward to your reply.

I'll give you an answer in a day or two.

I am looking forward to hearing from you at your earliest convenience.

I'm looking forward to hearing from you.

I have been waiting for your reply, but have not heard from you.

I'm looking forward to your reply.

I'm extremely embarrassed that it has taken so long to reply.

Please respond.

Your response is greatly appreciated and will enable us to prepare more efficiently.

I have not heard from you. I was wondering if maybe my mail never got to you.

I'm sorry for the delay in my reply.

Excuse me for not having answered your letter sooner.