If two vectors are given as $\vec{A}=-12\,\rm\hat i+8\,\rm\hat j$ and $\vec{B}=24\,\rm\hat i+18\,\rm\hat j$, determine the resultant vector $\vec{R}=2\vec{A}-\frac{1}{3}\vec{B}$, and also find its magnitude ($R\ or\ \left|R\right|$) and direction (angle $\theta $ between vector and horizontal line)