Vector Algebra

If $\vec{P}=b \hat{i}+6 \hat{j}+\hat{k} \quad$ and $\quad \vec{Q}=\hat{i}-a \hat{j}+4 \hat{k} \quad$ are perpendicular to each other, also $3 \mathrm{~b}-\mathrm{a}=5$. The value of $a$ and $b$ is