Consider a narrow band signal, propagating in a lossless dielectric medium $\left(\varepsilon_{r}=4, \mu_{r}=1\right)$, with phase velocity $v_{p}$ and group velocity $v_{g}$. Which of the following statement is true? ($c$ is the velocity of light in vacuum.)
- $v_{p} > c, v_{g} > c$
- $v_{p} < c, v_{g} > c$
- $v_{p} > c, v_{g} < c$
- $v_{p} < c, v_{g} < c$