When (S)-2-bromopropanoic acid [(S)−CH3CHBrCO2H] reacts with concentrated sodium hydroxide, the product formed (after acidification) is ( R )-2-hydroxypropanoic acid [(R)−CH3CHOHCO2H commonly known as (R)-lactic acid]. This is, of course, \right. the normal stereochemical result for an SN2 reaction. However. when the same reaction is carried out with a low concentration of hydroxide ion in the presence of Ag2O (where Ag+ acts as a Lewis acid), it takes place with overall retention of configuration to produce (S)-2-hydroxypropanoic acid. The mechanism of this reaction involves a phenomenon called neighboring-group participation. Write a detailed mechanism for this reaction that accounts for the net retention of configuration when Ag+ and a low concentration of hydroxide are used.