The cross product of two vectors in 2D is given by the determinant of the 2x2 matrix formed by the coefficients of $\hat{i}$ and $\hat{j}$ in the two vectors. So, we have
\[\vec{A} \times \vec{B} = \begin{vmatrix} \hat{i} & \hat{j} \\ 3 & 4 \\ -3 & 7 \end{vmatrix}
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