A new system of unit is evolved in which the values of $${\mu _0}$$ and $${ \in _0}$$ are 2 and 8 respectively. Then the speed of light in this system will be
The electric field associated with an electromagnetic wave in vacuum is given by $$E = \hat i40\cos \left( {kz - 6 \times {{10}^8}t} \right),$$ where $$E,z$$ and $$t$$ are in $$volt/m,$$ metre and second respectively. The value of wave vector $$k$$ is