Let $A(-1,1), B(3,4)$ and $C(2,0)$ be given three points. A line $y=m x, m>0$, intersects lines $A C$ and BC at point P and Q respectively. Let $\mathrm{A}_1$ and $A_2$ be the areas of $\triangle A B C$ and $\triangle P Q C$ respectively, such that $A_1=3 A_2$, then the value of $m$ is equal to :