Let A = \( \begin{bmatrix} {1} & {1} & 1 \\[0.3em] 3 & -1 & 1 \ \\[0.3em] 1& 5& 3 \\[0.3em] \end{bmatrix} \) and V be the vector space of all X ∈ R³ such that AX = 0.Then dim(V) is