An aryl halide such as

An aryl halide such as chlorobenzene can undergo a nuclephilic substitution reaction in the presence of a very strong base such as -NH2.
There are two surprising aspects to this reaction:the aryl halide does not have to contain an electron-withdrawing group,and the incoming substituent does not always end up on the carbon vacated by the leaving group.
For example,when chlorobenzene –with the carbon to which the chlorine is attached isotopically labeled with 14c-is reacted with amide ion in liquid ammonia,aniline is obtained as the product .
Half of the product has the amino group attached to the isotopically labeled carbon as expected,but the other half has the amino group attached to the carbon adjacent to the labeled carbon .
(a) Write the meachism for this reaction.
(b) What products will be obtained when chlorobenzene is replaced by o-bromotoluene (without 14C labeling) in this reaction?