Answer:
I guess that the atoms are:
Protons: 6 8 5 2 12 12
Neutrons: 8 8 5 3 13 14
Now, two atoms are isotopes if they share the same number of protons (so both atoms are the same element) but they have a different number of neutrons.
From the given options, the only two that have the same number of protons but a different number of neutrons are:
Protons 12, neutrons 13
and
Protons 12, neutrons 14.
These two are isiotopes.
So the problem are asking to find the value of G base on the formula of the said equation of the magnitude of gravitational attraction on either body. Base on that, the possible answer or the derived formula of the said function is G = Fr^2/m1m2. I hope you are satisfied with my answer and feel free to ask for more
the number of neutrons may b 21