A spacecraft transfers between three circular orbits by changing its speed four times. It starts in the medium-sized orbit (red; altitude \( =2000 \mathrm{mi} \) ), moves to the large orbit (blue; altitude \( =3000 \) mi ), then to the small orbit (green, altitude = 1000 mi ). The radius of the planet is 2000 mi and its mass is 0.4 times the mass of Earth, which has a radius of 3960 mi . Find the changes in speed (expressed in units of \( \mathrm{ft} / \mathrm{s} \) ). Find the changes in speed (expressed in units of \( \mathrm{ft} / \mathrm{s} \) ) at points \( A, B \), C, and D.
