I'm assuming the B1.1 course is a language course? Then it is possible, since you have to select 4 to 8 credits in "interdisciplinary qualification" modules, which include language courses.
If the subjects from the social science departement are masters courses, then you you shouls be able to add those to the supplement (that is so, if the last digit of the module number is a 7). Otherwise be aware, that you are only allowed to select at most 8 credits of bachelor modules in total.