The problem is about gravitational force, which means we have to use the universal law of gravitation.
[tex]F_{12}=G\cdot\frac{m_1\cdot m_2}{r^2_{12}}[/tex]Where G = 6.67x10^-11, m1 = 2.80 * 10^3, m2 = 9.75*10^ 10, and r = 28m. Let's replace these values
[tex]\begin{gathered} F_{12}=6.61\times10^{-11}N\cdot kg^{-2}m^2\cdot\frac{2.80\times10^3\operatorname{kg}\cdot9.75\times10^{10}\operatorname{kg}}{(28m)^2} \\ F_{12}=\frac{180.453\times10^2}{780}N \\ F_{12}\approx23.2N \end{gathered}[/tex]
