For an ellipse with eccentricity $\large\frac{1}{2}$ the center is at the orgin. If one directrix is $x=4$, then the equation of the ellipse is

Question

\[\begin {array} {1 1} (1)\;3x^2+4y^2=1 & \quad (2)\;3x^2+4y^2=12 \\ (3)\;4x^2+3y^2=1 & \quad (4)\;4x^2+3y^2=12 \end {array}\]