Sir Isaac Newton discovered that any 2 masses m1 and m2 attract each other with a force...

Sir Isaac Newton discovered that any 2 masses m₁ and m₂ attract each other with a force that is equal in magnitude and acts in the opposite direction, according to the following relationship:

where

F = attractive force, N

G = Universal Gravitational Constant

m₁ = mass of particle-1, kg

m₂ = mass of particle-2, kg

r = distance between the center of each particle, m

What is the appropriate unit for G, if the above equation is to be homogeneous in units?