Conservation of angular moment and crossing of orbits

The earth moves in a circular orbit with radius around the sun with speed . A comet also orbits the sun in a path such that the perihelion is at at a speed . The question is to deduce from the conversation of angular momentum that the angle at which their orbits cross is .

Now, I know that angular momentum is but I am unsure how to apply this to the question and I am unsure what is representing here. And do I also have to consider the momentum of the earth?