Electrochemical Cell Potentials Can Be Used to Determine Equilibrium Constants $\to$

Electrochemical cell potentials can be used to determine equilibrium constants that would be otherwise difficult to determine because concentrations are small.Calculate the value of K_sp for CdS from the following data.
CdS(s) + 2 e^- $\to$ Cd(s) + S^2-(aq)
E° = -1.21 V
Cd²⁺(aq) + 2 e^- $\to$ Cd(s)
E° = -0.40 V

A) 4.06 $\times$ 10^-55
B) 4.32 $\times$ 10^-28
C) 2.08 $\times$ 10^-14
D) 2.31 $\times$ 10²⁷
E) 2.47 $\times$ 10⁵⁴