112. Solving a chemistry problem

Monodisperse polystyrene latex (with a copolymer of methacrylic acid and sodium salt of vinylphenylsulfonate) with a particle diameter of 610 nm was studied by microelectrophoresis in an aqueous medium of 1.00 mmol/dm3 of potassium chloride KCl. At 25°C (and pH 7) the electrophoretic mobility was -4.05*10-8 m2/(s*V). Calculate the thickness of the DEL and the zeta potential, assuming ε = 78.35, η = 0.890 cP.