Dear Mr. Green, I was very concerned when I received your letter of yesterday complaining that the central heating system in your new house had not been completed by the date promised. After reading our earlier letters, I found that I had mistaken the date for completion. The fault is entirely mine and I deeply regret that it should have occurred. I realize the inconvenience our mistake must be causing you and will do everything possible to avoid any further delay. I have already given instructions for the worker and it will be soon solved. Yours faithfully, Andy Blair