Electromagnetic Waves

A plane electromagnetic wave of frequency 100 MHz is travelling in vacuum along the x-direction. At a particular point in space and time, $$\overrightarrow B = 2.0 \times {10^{ - 8}}\widehat kT$$. (where, $$\widehat k$$ is unit vector along z-direction) What is $$\overrightarrow E$$ at this point?