Acceleration and gravitational constant from two isolated spheres

[Miike012]

Two spheres of masses m1 = 1.00 g and m2 = 1.00 *10^2
kg are isolated from all other bodies and are initially at
rest, with their centers a distance r = 15.0 cm apart. One
minute later, the smaller sphere has moved 0.534 mm
toward the larger sphere. Compute the acceleration and G.

Solution:

No idea where to being.. some hints please?

 

[JHamm]

To start the two masses are so greatly different the problem seems to only want you to consider the small ball as moving. I'd begin by writing down the law of gravity and the definition of a force. With those you can probably find a way to calculate acceleration.