If α and β are the zeros of the polynomial f(x) = kx² + 4x + 4 such that α² + β² = 24, then find the positive value of k.
\( \frac{4}{3} \)
\( \frac{1}{3} \)
\( \frac{3}{4} \)
\( \frac{2}{3} \)
D. \( \frac{2}{3} \)