Dear Sir, I am sorry that I didn't answer before, but we were very busy. We would be very happy to work with you. (I´m unsure what was meant in the sentence that was next) The Peruvian cotton is the finest quality and we are sure that you will be happy with our workmanship. If you are in agreement, we are awaiting your reply and would be pleased to work with you.

"If you agree, please contact me as soon as possible." - I agree, that sounds better.

I would suggest a mixture of both Eddy's and aloshek's post, as they are both outstanding. (The only question from my view is the comment on "Peruvian cotton") It may have two definitions. Example: Is it your factory's Peruvian cotton that is the best quality, compared to Peruvian cotton at other manufacturers. Or is Peruvian cotton better quality compared to Egyptian cotton or American cotton. That said, this is my synthesis of the previous two posts. . .

"Dear Sir,

I´m sorry, that I could not answer you earlier but we were very busy. We would be very happy to work with you. We manufacture cotton underwear and T-shirts. The Peruvian cotton is the finest quality and we are sure that you will be happy with our workmanship. If you agree, please contact me as soon as possible.

Respectfully,

"