Consider the series: $$\sum_{k=3}^{\infty} \left( \dfrac{3}{(k-1)^{2}} - \dfrac{3}{k^{2}} \right)$$ a) Determine whether the series is convergent or divergent: .
(Enter "convergent" or "divergent" as appropriate.)

b) If it converges, find its sum: .
If the series diverges, enter here "divergent" again.