Relation between E and B in an EM wave

2022 Phase 2 2 questions

1. The magnetic field of a plane electromagnetic wave is given by $\vec{B}=3\times10^{-8}\cos(1.6\times10^{3}x+48\times10^{10}t)\hat{j}$, then the associated electric field will be:
2. The ratio of the magnitude of the magnetic field and electric field intensity of a plane electromagnetic wave in free space of permeability $\mu_0$ and permittivity $\varepsilon_0$ is (Given that c - velocity of light in free space)