Getting a rhombus vertex knowing one vertex and its area

Hi there. Im tryin to solve this one, I know that if I find the way to get one more vertex i'd have it solved.

*The point A(-1,8) is the vertex of a rhombus which minor diagonal is situated on the line L: *

, . Get the coordinates of the rest of the vertex knowing that the rhombus area is 30.

Well, I haven't done too much. Actually I did some, but then I realized that I had confused something, cause I got the line L' where would be located the major D, but I've used for it the point A, and then I was trying to get the point of intersection between L and L', so then I doubled it, and I was going to get my second vertex, but then I realized that it was wrong, cause I couln't use point A, cause A don't belongs to L', it belongs to L, so...

So, I don't know much about L', but that its perpendicular to L.