Question

find the force of gravitation between two objects weighing 450kg and 570kg when they are 0.750 m apart

Answer 1

If one can assume objects as material points,
F = G m₁ m₂ /r²⁼6.67*10^-11*450*570/0.75^2=3*10^-5 N
otherwise force will be strongly dependent on shape and mass distribution inside objects.