A huge balloon and its gondola, of mass M, are in the air and stationary with respect to the ground.

A huge balloon and its gondola, of mass M,
are in the air and stationary with respect to the ground. A passenger, of mass
m, then climbs out and slides down a rope with speed v, measured with respect
to the balloon. With what speed and direction (relative to Earth) does the
balloon then move? What happens if the passenger stops?