Complex Numbers

If z and \(\omega\) are two complex numbers such that \(\left| {z\omega } \right| = 1\) and \(\arg (z) - \arg (\omega ) = {{3\pi } \over 2}\), then \(\arg \left( {{{1 - 2\overline z \omega } \over {1 + 3\overline z \omega }}} \right)\) is :

(Here arg(z) denotes the principal argument of complex number z)