Calculating the Molarity of an Ion?

I'm completely stuck on this one - I was doing an experiment in a lab and now I cannot find the molarity of an ion in a solution. I've looked everywhere on the web but after 2 hours of searching I couldn't find anything. Maybe I am looking in the wrong direction. 


I mixed three solutions: 1mL of $\ce{0.1M ~CuSO4}$, $\ce{0.28 M ~~NH3}$ and water.
This solution turned into


$$\ce{Cu(H2O)4^{2+} + 4NH3 = Cu(NH3)4^{2+} + 4H2O}$$


This turned the solution from light blue to dark blue-ish purple. The final mL of the mixed solutions was 25 mL.
Now I am supposed to calculate the molarity of the $\ce{Cu(NH3)4^{2+}}$ ion. I am pretty sure that I only have to calculate the molarity of $\ce{Cu^{2+}}$ but I am not entirely sure. If you guys could give me some help on this I would be very grateful. 


