Which of the following aqueous solutions has osmotic pressure nearest to that of an equimolar solution of K4[Fe(CN)6]

We know that the value of colligative property is directly proportional to number of particles of solute. Since K4[Fe(CN)6] and Al2(SO4)3 both form 5 ions on dissociation. Hence osmotic pressure of Al2(SO4)3 solution will be nearest to that of equimolar solution of K4[Fe(CN)6]