Let $w = x ^ { 2 } + y ^ { 2 } + z ^ { 2 }$

Multiple Choice

Let $w = x ^ { 2 } + y ^ { 2 } + z ^ { 2 }$ with constraint $x ^ { 2 } + 4 y ^ { 2 } = 16$ . Then the minimum value of w is

A) 24
B) 23
C) 19
D) 17
E) 16