A 15.0 mL sample of a solution is tested for Cl^– ions. Two drops (1 drop ≈ 0.2 mL) of 0.15 M AgNO₃ were added to the solution. Calculate the minimum mass (in g) of the Cl^– ion that should be present for AgCl(s) (K_sp = 1.8 × 10^–10) to form.