Answer
See answers.
Work Step by Step
a. Section 33–2 says that a white dwarf of 1 solar mass is about the size of Earth, so $r\approx 6380 km$.
Section 33–2 says that a neutron star of 1.5 solar masses has a diameter of 20 km, so a radius of about 10 km.
To find the radius of a black hole of 3 solar masses, calculate the Schwarzschild radius.
$$R=\frac{2GM}{c^2}$$
$$=\frac{2(6.67\times10^{-11}Nm^2/kg^2)3(1.99\times10^{30}kg)}{(3.00\times10^8 m/s)^2}=8.85km$$
b. The ratios are 6380:10:8.85, or roughly 721:1.1:1, or to one significant figure, about 700:1:1.
