Are those definitions of vectors being a vector normal to the plane given? If so, the vectors are not unique, unless it's understood they go through the origin and are unit vectors, or something like that.
Part i) does not parse grammatically - I have no idea what's being asked there. "de" is not a word in the English language, that I'm aware of.
Part ii) makes sense only if you've correctly solved part i).
A little more clarification would be nice!