Solve the Problem A) 10
B) 4
C) 2
D) 1

Multiple Choice

Solve the problem.
- $\text { Find the maximum value of } f ( x , y , z , w ) = x + y + z + w \text { subject to } x ^ { 2 } + y ^ { 2 } + z ^ { 2 } + w ^ { 2 } = 1 \text {. }$

A) 10
B) 4
C) 2
D) 1