A precipitate forms when 50.0 mL of 0.200 M Pb(NO₃)₂(aq) is combined with 80.0 mL of 0.150 M Na₂S(aq) according to the reaction Pb²⁺(aq) + S²⁻(aq) → PbS(s). After precipitation is complete, what is the concentration of NO₃⁻(aq) in the remaining solution?
a) 0.100M
b) 0.077M
c) 0.154M
d) 0.169M