Minimize $F = x ^ { 2 } + y ^ { 2 }$

Multiple Choice

Minimize $F = x ^ { 2 } + y ^ { 2 }$ with $x + 2 y = 20$ .

A) $F = 2$
B) $F = 20$
C) $F = 80$
D) $F = 72$
E) $F = 60$