If 135g of NiCl₂ $\left[ \mathrm { Ni } \left( \mathrm { NH } _ { 3 } \right) _ { 6 } \right] ^ { 2 + }$

If 13.5g of NiCl₂.6H₂O is added to 500mL of 1.50M aqueous ammonia, what is the equilibrium concentration of Ni²⁺(aq) ? The complex formed is $\left[ \mathrm { Ni } \left( \mathrm { NH } _ { 3 } \right) _ { 6 } \right] ^ { 2 + }$ Given K_f = 5.5×10⁸.

A) 5.4×10^-10
B) 6.7×10^-9
C) 1.5×10^-10
D) 8.7×10^-8
E) 2.1×10^-9