Lorentz invariants


In a certain reference frame a static uniform electric field E0 is at an angle θ0 ≠ π/2 to a static, uniform, magnetic induction B0, (B0 = E0/c), in the SI system of units.
(a)  Determine the magnitude of E and B in a reference frame in which the angle between E and B is θ.
(b)  Is there a reference frame for which E and B are perpendicular to each other?  If so, what is it?