Write each of the given numbers in the polar form $re^{i\theta}$, $- \pi < \theta \le \pi$.
(a) $\displaystyle \frac{2-i}{6}$
$r =$ , $\theta =$ ,
(b) $-3\pi(7+i\sqrt{3})$
$r =$ , $\theta =$ ,
(c) $(1+i)^5$
$r =$ , $\theta =$ .