# Normal vector in Phong Illumination Model should be normalized?

I'm studying Illumination subject these days and I was given a problem which asks to calculate the intensity using phong illumination model. I'm little bit confused whether I should calculate normal vector using after normalize it or as it is. Normal is given below. So if you can please tell me what type of vector I have to use there and if I have to use normalized vectors then it's value.

$N=(0,0,-12)$