Write a Polar Equation In $r$ And $\theta$ Of an Ellipse with the Focus at the Origin, with Ellipse

Write a polar equation in $r$ and $\theta$ of an ellipse with the focus at the origin, with the eccentricity $\frac { 6 } { 7 }$ and directrix $x = - 13$ .

A) $r = \frac { 78 } { 7 - 6 \cos \theta }$
B) $r = \frac { 13 } { 7 + 6 \cos \theta }$
C)
$r = \frac { 78 } { 1 - 6 \cos \theta }$
D)
$r = \frac { 78 } { 7 + 6 \cos \theta }$
E)
$r = \frac { 6 } { 3 - 6 \sin \theta }$