Consider the Cell: Ni(s)∣ Ni²⁺ (Aq,?M) Cu²⁺ (Aq,0.136 M)∣ Cu(s)

Consider the cell:
Ni(s) ∣ Ni²⁺ (aq,?M) Cu²⁺ (aq,0.136 M) ∣ Cu(s)
Ni²⁺(aq) /Ni(s) E° = -0.257 V Cu²⁺(aq) /Cu(s) E° = 0.340 V
The measured potential of the cell is 0.621 V.What is [Ni^2+] at 25 °C?

A) 2 × 10^-2 M
B) 1 M
C) 4 × 10^-42 M
D) 0.05 M
E) 0.4 M