Don't see any reason why the office job should be charged at a lower rate than your dom jobs. I used to charge the same rate for my Solicitors office cleaning job as I did my dom jobs. I added on parking fees as it was a town centre job. As I was supplying materials I obviously charged them for that too, plus added on a little bit extra as I was the one collecting them.
The biggest hassle was in respect that it was a 3 hour shift to be carried out during normal working hours, but if I didn't get there before 9 I had no chance of getting a parking space nearby that allowed me to park for 3 hours (most were 2 hour max spaces). That caused problems on a fairly regular basis, as I had quite a way to travel to get to the office and found I was driving round looking for adequate parking spaces. I also found it difficult to clean as the Solicitors had had problems with their previous cleaners so wanted me in their during office hours, and that proved impossible to clean properly as I was constantly trying to clean around peoples legs etc etc.
I also had another office job which necessitated the visit to be in the evening or weekend. So price your job to take this into account.
Really it all depends if you want to take on this type of work. I don't know what sort of reputation office cleaning companies have in your area, but I have found that I was getting quite a few calls from disgruntled office peeps who were unhappy with the cleaners they had employed, so I could have taken on quite a few office cleaning contracts. I decided, tho, that I would rather concentrate on dom cleaning as I was getting plenty of work in that area (and still am).
Before I quote anything tho, Maggie, I would go along and price up the job accordingly.
Good luck!
Jan