If the radius of the circle $x^2 + y^2 - 18x + 12y + k = 0$ is $11$,then $k = $

Let a circle passing through $(2,0)$ have its centre at the point $(h, k)$. Let $(x_c, y_c)$ be the point of intersection of the lines $3x + 5y = 1$ and $(2+c)x + 5c^2y = 1$. If $h = \lim_{c \to 1} x_c$ and $k = \lim_{c \to 1} y_c$,then the equation of the circle is:

The equation of the circle with centre $(1, 2)$ and tangent $x + y - 5 = 0$ is

The equation of the circle whose diameters have the end points $(a, 0)$ and $(0, b)$ is given by:

The parametric equations of the circle $x^2+y^2-6x-2y+9=0$ are

If the parametric equations of the circle passing through the points $(3,4)$,$(3,2)$,and $(1,4)$ are $x=a+r \cos \theta$ and $y=b+r \sin \theta$,then find the value of $b^{a} r^{a}$.