a)
In order to calculate this force, we can use the formula below:
[tex]F=\frac{G\cdot M\cdot m}{d^2}[/tex]Where G is the gravitational constant, M is the bigger mass, m is the smaller mass, and d is the distance between each one.
So, for G = 6.674*10^−11, M = 5.98*10^24 kg, m = 58.4 kg and d = 6.38*10^6 m, we have:
[tex]\begin{gathered} F=\frac{6.674\cdot10^{-11}\cdot5.98\cdot10^{24}\cdot58.4}{(6.38\cdot10^6)^2} \\ F=\frac{2330.774\cdot10^{13}}{40.704\cdot10^{12}} \\ F=573\text{ N} \end{gathered}[/tex]b)
Sally's weight is equal to the previously calculated force:
[tex]W=F=573\text{ N}[/tex]If we use a value of gravity of 9.81, we can get approximately the same value:
[tex]\begin{gathered} W=m\cdot g \\ W=58.4\cdot9.81 \\ W=573\text{ N} \end{gathered}[/tex]