In an excess of `NH_(3(aq.)),Cu^(2+)` ion form a deep blue complex ion `[Cu(NH_(3))_(4)]^(2+)` having formation constant `K_(f)=5.6xx10^(11)`. Calculate the concentration of `Cu^(2+)` in a solution prepared by adding `5.0xx10^(-3)` mole of `CuSO_(4)` to `0.50` litre of `0.40M NH_(3)`.