Factor Completely $$a ^ { 2 } - 40 a b + 400 b ^ { 2 }$$

Multiple Choice

Factor completely.
- $$a ^ { 2 } - 40 a b + 400 b ^ { 2 }$$

A) $( a - 20 b ) ^ { 2 }$
B) $( a + 20 b ) ( a - 20 b )$
C) $( a + 20 b ) ^ { 2 }$
D) Prime