[NTG-context] Two minor questions

Dear list, I have 2 small questions: 1. In \setuplayout if I try to set topspace=5\measured{base} + \dimexpr2bp I get an error. How should I add these 2bp? 2. I have an mp graphic defined in the file "graphic.mp" which has the exact same dimensions as my page. I'd like to set that graphic as a background. How do I do this?