If $\vec{a} = \hat{i} + 2 \hat{j} + 3 \hat{k}$ and $\vec{b} = 2 \hat{i} + 4 \hat{j} - 5 \hat{k}$ represent two adjacent sides of a parallelogram, find unit vectors parallel to the diagonals of the parallelogram.ORUsing vectors, find the area of the triangle $ABC$ with vertices $A(1,2,3)$, $B(2,-1,4)$ and $C(4,5,-1)$.