Vector Algebra

If $\mathbf{a}=\hat{\mathbf{i}}-2 \hat{\mathbf{j}}+2 \hat{\mathbf{k}}$ and $\mathbf{b}=9 \hat{\mathbf{i}}+6 \hat{\mathbf{j}}-18 \hat{\mathbf{k}}$ are two vectors, then $\frac{\text { Projection of } \mathbf{b} \text { on } \mathbf{a}}{\text { Projection of } \mathbf{a} \text { on } \mathbf{b}}=$