Calculate the concentration of chloride ions in a saturated lead

PbCl2 (s) <=> Pb2+ (aq) + 2 Cl- (aq) 

for which the equilibrium requirement is 

Ksp = [Pb2+][Cl-]^2 

Let x = mol/L PbCl2 that dissolves to estabilish equilibrium. 
This will produce x mol/L Pb2+ and 2x mol/L Cl- 
This gives us at equilibrium : 
[Pb2+]= x and [Cl-]= 2x = 6.2 x 10^-4 mol/L 
x = [Pb2+] = 6.2 x 10^-4 / 2 = 3.1 x 10^-4 mol/L 

Ksp = (3.1 x 10^-4)( 6.2 x 10^-4)^2 =1.2 x 10^-10

North atlantic current or north atlantic drift is the answer

Carbon based or cells?