\[b_{1} = - \frac{1}{3};\ \ q = - 3;\]
\[b_{2} = b_{1}q = - \frac{1}{3} \cdot ( - 3) = 1;\]
\[b_{3} = b_{2}q = 1 \cdot ( - 3) = - 3;\]
\[b_{4} = b_{3}q = - 3 \cdot ( - 3) = 9.\]
\[b_{5} = b_{4}q = 9 \cdot ( - 3) = - 27.\]