Chemistry Question?

                           AgCl(s) ⇌ Ag⁺(aq) + Cl⁻(aq)      Ksp = 1.8 × 10⁻¹⁰
Initial (mol L⁻¹)        ----            0              0
Change (mol L⁻¹)    ----          +s            +s
Eqm (mol L⁻¹)          ----           s              s

At equilibrium:
Ksp = [Ag⁺] [Cl⁻]
1.8 × 10⁻¹⁰ = s²
s = √(1.8 × 10⁻¹⁰)
s = 1.3 × 10⁻⁵

The answer:  1.3 × 10⁻⁵ mol L⁻¹ (the 5th option)