(d) $\frac{c^{2}}{v^{2}} = \frac{\mu}{\mu_{0}} \bullet \frac{\varepsilon}{\varepsilon_{0}}$
$\therefore\frac{\varepsilon}{\varepsilon_{0}} = \frac{9 \times 10^{16}}{4 \times 10^{16}} \times \frac{4\pi \times 10^{- 7}}{5 \times 10^{- 7}} = 5.8 \approx 6$