Let \( 0<\alpha<1, \; \beta=\frac{1}{3\alpha} \) and \( \tan^{-1}(1-\alpha)+\tan^{-1}(1-\beta)=\frac{\pi}{4} \). Then \( 6(\alpha+\beta) \) is equal to:
\( 6 \)
\( 7 \)
\( 8 \)
\( 9 \)