7. Europa, one of Jupiter's moons, is roughly spherical. The equatorial radius of Europa is about 1,600,000 meters, and the mass of Europa is about
48,000,000,000,000,000,000,000 kilograms.
a. Find the order of magnitude of the radius r of Europa, and the order of
magnitude of the mass m of Europa.
b. Find the order of magnitude of the volume V of Europa.
c. Use the orders of magnitude of mand V that you found in parts (a) and
(b) to approximate the average density d (in kilograms per cubic meter)
of Europa using the formula d = m.​