Let $A ( a , 0 ) , B ( b , 2 b + 1 )$ and $C ( 0 , b ) , b \neq 0 , | b | \neq 1$, be points such that the area of triangle $A B C$ is 1 sq. unit, then the sum of all possible values of $a$ is:
(1) $\frac { - 2 b } { b + 1 }$
(2) $\frac { 2 b ^ { 2 } } { b + 1 }$
(3) $\frac { - 2 b ^ { 2 } } { b + 1 }$
(4) $\frac { 2 b } { b + 1 }$