ok back to what jambaugh said draw the vector a, and draw c that's perpendicular to it. see anything interesting? are the components of a sort of the components of c?
and also draw another vector oposite of c, how could a's components be related to d?
Also if you're given a vector c/d but you need it in a specific length but same direction as c/d then you solve for a new vector v = m(c or d/length of c or d) where m is the given length that they want.
 To be honest, I'm not sure if it's from a huge lack of sleep or not, but I'm just not grasping this one for some reason. I gather that the components of c would more than likely be somewhat close to those of a since they are perpendicular, but I'm not quite sure the relation of them. I'm not sure why I'm struggling with this problem so much.
