Write general expressions

Write general expressions for the electric and magnetic fields of a 1-GHz sinusoidal plane wave traveling in the y-direction in a lossless nonmagnetic medium with relative permittivity ?r = 9. The electric field is polarized along the x-direction, its peak value is 6 V/m and its intensity is 4 V/m at t = 0 and y = 2 cm.