#### Answer

$28$, $(-7,-14)$, $(-7,14)$

#### Work Step by Step

Given $4p=-28$, we have $p=-7$ and the equation becomes $y^2=-28x$ with focus at $(-7,0)$. The Latus Rectum is the length of the line segment between the intersection points when drawing a vertical line passing through the focus. We have $x=-7$, $y^2=196$, and $y=\pm14$. The length of the Latus Rectum is $|4p|=28$ and the endpoints are $(-7,-14)$ and $(-7,14)$