\( {}^{n-1}C_r = (k^2 - 8)\, {}^{n}C_{r+1} \) if and only if:
\( 2\sqrt{3} < k < 3\sqrt{3} \)
\( 2\sqrt{3} < k \le 3\sqrt{2} \)
\( 2\sqrt{2} < k < 2\sqrt{3} \)
\( 2\sqrt{2} < k \le 3 \)