A sinusoidal electromagnetic wave is propagating in a vacuum in the +z-direction

A sinusoidal electromagnetic wave is propagating in a vacuum in the +z-direction. If at a particular instant and at a certain point in space the electric field is in the +x-direction and has a magnitude of 4.00 V/m,

  1. what is the magnitude of the magnetic field of the wave at this same point in space and instant in time?
  2. What is the direction of the magnetic field?