What is the value of $\frac{\text{projection of } \vec{a} \text{ on } \vec{b}}{\text{projection of } \vec{b} \text{ on } \vec{a}}$ for vectors $\vec{a}=2\hat{i}-3\hat{j}-6\hat{k}$ and $\vec{b}=2\hat{i}-2\hat{j}+\hat{k}$?