If \(z=-(2 a+1)+2 a i\), where \(a\) is a non-zero real constant, then \(\dfrac{4 a}{1+\bar{z}}\) is equal to
- \(\sqrt{2} \text{cis}\left(\dfrac{\pi}{4}\right)\)
- \(\sqrt{2} \text{cis}\left(\dfrac{3 \pi}{4}\right)\)
- \(\text{cis}\left(\dfrac{\pi}{4}\right)\)
- \(\sqrt{2} \text{cis}\left(-\dfrac{3 \pi}{4}\right)\)
- \(\text{cis}\left(-\dfrac{\pi}{4}\right)\)