$\begin{array}{1 1} 0.81 \times 10^{-8} \text{which is very small, hence feasible} \\ 0.81 \times 10^{8} \text{which is very large, hence feasible} \\ 0.45 \times 10^{-8} \text{which is small, hence feasible} \\ 0.45 \times 10^{8} \text{which is large, hence not feasible} \end{array} $