Let $H \subset \mathbb Z^4$ be the group generated by the elements $(3, 9, 3, 0)$ and $(4, 2, 0, 2)$. Find the rank and the elementary divisors of $A := \mathbb Z^4 / H$.
I know how to find this when given n n-sized elements for $\mathbb Z^n$ but now I am confused since the algorithm I use makes use of an $n\times n$ matrix to find the elementary divisors. How do I do it in this case?
Thanks in advance for your help.