Marvin the Martian finally decides he’d like visit Venus rather than just stare at it through a telescope (hopefully the Earth will not get in the way this time!). How fast will his spacecraft need to travel in km/hr if he uses his 6 months of vacation time to travel to Venus (a = 0.72 AU) from Mars (a = 1.52 AU) and back again, stopping only briefly to take pictures? (Assume that Mars and Venus have circular orbits and are at their closest approach: you can then use their semi-major axes to determine the distance between the two.)