Identify the Center and Radius of the Circle $$x ^ { 2 } - 8 x + y ^ { 2 } = 20$$

Identify the center and radius of the circle. $$x ^ { 2 } - 8 x + y ^ { 2 } = 20$$

A) Center: $( 0 , - 4 ) ; r = 6$
B) Center: $( 4,0 ) ; r = 6$
C) Center: $( 8,0 ) ; r = 36$
D) Center: $( 8,0 ) ; r = 2 \sqrt { 5 }$