Suppose $3$ bulbs are selected at random from a lot. Each bulb is tested and classified as defective $(D)$ or non-defective $(N)$. Write the sample space of this experiment?

Given $3$ bulbs are to be selected at random from the lot. Each bulb in the lot is tested and classified as defective $(D)$ or non-defective $(N)$
The sample space of this experiment is given by, 
$S=DDD,DDN,DND,DNN,NDD,NDN,NND,NNN$