(a) Find the equation of the circle whose diameter has endpoints (-8, 2) and (2, 6). Write it in the form $$(x-h)^2 + (y-k)^2 = r^2$$ and identify $h$, $k$, and $r$.

$h$	=
$k$	=
$r$	=

(b) Find the equation of the circle that has center $(6,-4)$ and is tangent to the $y$-axis. Write it in the form $$(x-h)^2 + (y-k)^2 = r^2$$ and identify $h$, $k$, and $r$.

$h$	=
$k$	=
$r$	=