<span><em>Density</em>-dependent <em>factors</em> operate only when the population <em>density</em> reaches a certain level. </span>
Weight = (mass) x (gravity)
Weight = (7.0 kg) x (gravity)
On Earth, where (gravity) is roughly 10 N/kg . . .
Weight = (7.0 kg) x (roughly 10 N/kg)
Weight = roughly 70 Newtons
That's <em>B </em>on Earth.
It would be some other number on other bodies.