Sort of a tricky physics problem, electicity & magnetism AND mechanics?

[Phil H]

My entire AP Physics class worked on this for the entire hour today, and no one has been able to do it, but it's being collected tomorrow, so I kind of need some help to figure it out. If someone knows how to do it and could give a step-by-step way to arrive at the solution, or even just wanted to drop some advice that would be amazing.

The Problem: Two insulating spheres having radii 0.300 cm and 0.500 cm, masses 0.100 kg and 0.700 kg, and charges -2.00 µC and 3.00 µC are released from rest when their centers are separated by 1.00 m. (a) How fast will each be moving when they collide? (Hint: Consider conservation of energy and linear momentum) (b) If the spheres were conductors would the speeds be larger or smaller than those calculated in part (a)? Explain.

The Answers:
Part (a): 10.8 m/s and 1.55 m/s.
Part (b): Larger, but I don't know how to explain why.