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