When the 3-bromo-2-butanol with the stereochemical structure A is treated with concentrated HBr, it yields meso-2,3-dibromobutane; a

Question:

When the 3-bromo-2-butanol with the stereochemical structure A is treated with concentrated HBr, it yields meso-2,3-dibromobutane; a similar reaction of the 3-bromo-2-butanol B yields ({)-2,3-dibromobutane. This classic experiment performed in 1939 by S. Winstein and H. J. Lucas was the starting point for a series of investigations of what are called neighboring group effects. Propose mechanisms that will account for the stereochemistry of these reactions.