Of the five salts listed below, which has the highest concentration of its cation in water? assume that all salt solutions are saturated and that the ions do not undergo any additional reactions in water.

First of all, I need to know what these five salts are. Luckily, I found a similar problem from another website which is shown in the attached picture. The Ksp is the solubility product constant. It follows the formula:

Ksp = [cation concentration]ᵃ[anion concentration]ᵇ
where a and b are the subscripts of the metal and nonmetal, respectively. 

For the solutions ahead, let x be the concentration of the cation.

A.  The formula is PbCr₂O₄.
2.8×10⁻¹³ = [x][x]
Solving for x, x = 5.29×10⁻⁷ M

B. The formula is Co(OH)₂. 
 1.3×10⁻¹⁵ = [x][x]²
Solving for x, x = 1.09×10⁻⁵ M

C. The formula is CoS. 
 5×10⁻²² = [x][x]
Solving for x, x = 2.24×10⁻¹¹ M

D. The formula is Cr(OH)₃. 
 1.6×10⁻³⁰ = [x][x]³
Solving for x, x = 3.56×10⁻⁶ M

E. The formula is Ag₂S. 
 6×10⁻⁵¹ = [x]²[x]
Solving for x, x = 1.82×10⁻¹⁷ M

Thus,the highest concentration is letter B, Cobalt (II) Hydroxide.