17. (12 points) In $\triangle \mathrm { ABC }$, the sides opposite to angles $\mathrm { A } , \mathrm { B }$, C are $a , b , c$ respectively. The vector $\vec { m } = ( a , \sqrt { 3 } b )$ is parallel to $\vec { n } = ( \cos \mathrm { A } , \sin \mathrm { B } )$.\\
(I) Find A;\\
(II) If $a = \sqrt { 7 } , b = 2$, find the area of $\triangle \mathrm { ABC }$.