Finding vector magnitude and point coordinates from diagram

[mr_coffee]

Hello everyone, I'm not sure if i drew this right...I'm also confused on how I'm suppose to determine the coordinates of P. Thanks!

Here is the picture and directions:
http://img204.imageshack.us/img204/7265/ex36nk.jpg

 

[Doc Al]

No, it's not drawn correctly. The line L must be perpendicular to line a, yet pass through point b.

One way to find the coordinates of point P is to write the equations of the two lines and find where they intersect.