$3\times {\text{10}}^{\text{41}}\text{kg}$

(a) $3\times {\text{10}}^{\text{52}}\text{kg}$

(b) $2\times {\text{10}}^{\text{79}}$

(c) $4\times {\text{10}}^{\text{88}}$

0.30 Gly

(a) $2\text{.}0\times {\text{10}}^5\text{km/s}$

(b) $0\text{.}\text{67}c$

$2\text{.}7\times {\text{10}}^5\text{m/s}$

$6\times {\text{10}}^{-\text{11}}$ (an overestimate, since some of the light from Andromeda is blocked by gas and dust within that galaxy)

(a) $2\times {\text{10}}^{-8}\text{kg}$

(b) $1\times {\text{10}}^{\text{19}}$

(a) $30\text{km/s}\cdot \text{Mly}$

(b) $15\text{km/s}\cdot \text{Mly}$

960 rev/s

$\text{89}\text{.}\text{999773º}$ (many digits are used to show the difference between $\text{90º}$)

23.6 km

(a) $2\text{.}\text{95}\times {\text{10}}^{\text{12}}\text{m}$

(b) $3\text{.}\text{12}\times {\text{10}}^{-4}\text{ly}$

(a) $1\times {10}^{20}$

(b) 10 times greater

(a) $v=H_{0}d=(20\text{ km/s})/\text{Mly }(2.00\times {10}^2\text{ Mly})=4.00\times {10}^3\text{ km/s}$

(b) $\begin{array}{l}d=\sqrt{{(1.00\times {10}^2)}^2+{(2.00\times {10}^2)}^2}\text{ Mly}\\ =2.24\times {10}^2\text{ Mly}\\ v=(20\text{ km/s})/\text{Mly }(2.24\times {10}^2\text{ Mly})=4.48\times {10}^3\text{ km/s}\end{array}$

(c) The galaxies are separating mostly due to the expansion of space.

(d) Light from the third galaxy would have a red shift when detected in either of the other galaxies.