What is the [Cu2+] in the cell Zn(s) | Zn2+(1.0 M) || Cu2+(aq) | Cu(s) The standard emf of the cell is 1.10 V. Ecell = 1.03 V.?

Balance equation for the cell reaction:
Zn(s) + Cu²⁺(aq) → Zn²⁺(aq) + Cu(s)

Nernst equation:
Ecell = E°cell - (0.0592/n) log₁ₒ([Zn²⁺]/[Cu²⁺])
1.03 = 1.10 - (0.0592/2) log₁₀(1.0/[Cu²⁺])
0.0296 log₁₀(1.0/[Cu²⁺]) = 0.07
log₁₀(1.0/[Cu²⁺]) = 2.37
log₁₀[Cu²⁺] = -2.37
[Cu²⁺] = 10⁻²·³⁷ M
[Cu²⁺] = 0.004 M

The answer: b. 0.004 M