For the following reaction, the equilibrium constant Kc at 298 K is 1.6 × 10¹⁷: Fe²⁺(aq) + S²⁻(aq) ⇌ FeS(s). When equal volumes of 0.06 M Fe²⁺(aq) and 0.2 M S²⁻(aq) solutions are mixed, the equilibrium concentration of Fe²⁺(aq) is found to be Y × 10⁻¹⁷ M. The value of Y is ______