On one side of an overhanging swing, 3 meters from the axle, sits a girl Nina weighing 21 kg. On the other side, her sister Jane with a mass of 30 kg occupies the same position. Due to her weight, Jane drops 70 cm to the ground with a swing in a slow squat, and her sister lifts the swing into the air. By how much does each of them increase or decrease in potential energy?
and Jane's decreases by 
.
