One of the asteroids, Asty, looks like an elongated potato. Surprisingly it has a tiny (compared to Asty) spherical moon! This moon called Dactyl has a mass of 4.20x1016kg, and a radius of 1.57x104 meters, according to Wikipedia. You are supposed to orbit a space probe around the moon to measure its optical properties. If you are 10,000 meters above the surface, what must your orbital speed be?