If the locus of $z \in \mathbb{C}$, such that $\operatorname{Re}\left(\frac{z-1}{2 z+i}\right)+\operatorname{Re}\left(\frac{\bar{z}-1}{2 \bar{z}-i}\right)=2$, is a circle of radius $r$ and center $(a, b)$, then $\frac{15 a b}{r^2}$ is equal to :

If the center of a regular hexagon is at the origin and one of the vertices on the Argand diagram is $1 + 2i$,then its perimeter is

Let $S=S_1 \cap S_2 \cap S_3$,where $S_1=\{z \in \mathbb{C}:|z|<4\}$,$S_2=\{z \in \mathbb{C}: \operatorname{Im}[\frac{z-1+\sqrt{3} i}{1-\sqrt{3} i}]>0\}$,and $S_3=\{z \in \mathbb{C}: \operatorname{Re} z>0\}$.
$1.$ Area of $S=$
$(A) \frac{10 \pi}{3} \quad (B) \frac{20 \pi}{3} \quad (C) \frac{16 \pi}{3} \quad (D) \frac{32 \pi}{3}$
$2.$ $\min _{z \in S}|1-3 i-z|=$
$(A) \frac{2-\sqrt{3}}{2} \quad (B) \frac{2+\sqrt{3}}{2} \quad (C) \frac{3-\sqrt{3}}{2} \quad (D) \frac{3+\sqrt{3}}{2}$

Let $\left|\frac{\bar{z}-i}{2 \bar{z}+i}\right|=\frac{1}{3}$,where $z \in \mathbb{C}$,be the equation of a circle with center at $C$. If the area of the triangle,whose vertices are at the points $(0,0)$,$C$,and $(\alpha, 0)$,is $11$ square units,then $\alpha^2$ equals

If $|z - 2|/|z - 3| = 2$ represents a circle,then its radius is equal to

The number of elements in the set $\{ z = a + ib \in \mathbb{C} : a, b \in \mathbb{Z} \text{ and } 1 < |z - 3 + 2i| < 4 \}$ is: