We have received your mail and sorry to reply you so late. For your detail question, it's still under discussing, so I can't give you answer right now. Pls wait for more days, and I will reply you as soon as I got the result, thanks.
“对你所说的,我们这边还在商量”: 这句话跟前面的意思重复了,所以不建议再写一遍,商务信函不能啰唆哈!
i have received your letter already,sorry for the delay of the reply,because we are still under the discussion on the some detailed matter.sorry again for making you wait.for what you required,we 'll let you know the result a couple of days later after the discussion.