The problem says only one person can drive. We can choose $2$ people from the remaining $4$ to join S and J in the back seat in $\binom{4}{2}$ ways. The $4$ people in the back seat can arrange themselves in $4!$ ways, and the $2$ non-drivers in front can arrange themselves in $2!$ ways, for a total of $\binom{4}{2}4!2!$.