Chapter 5, Problem 5.12P

Given $\text{E}=120\pi \cos \left(6\pi \times {10}^{6}t-0.080\pi y\right){\text{a}}_z\text{V/m}$ and $\text{H}=2.00\cos \left(6\pi \times {10}^{6}t-0.080\pi y\right){\text{a}}_x\text{A/m}$, find ${\text{μ}}_{\text{r}}$ and ${\text{ε}}_{\text{r}}$.