The Sylow Theorems · Hard problem

A group $G$ has order $52$. Its Sylow $2$-subgroup $P$ (order $4$) is self-normalizing: $N_G(P) = P$, so $|N_G(P)| = 4$. What is $n_2$, the number of Sylow $2$-subgroups of $G$?