Provide an Appropriate Response $f(x, y)$ , Then How Should We Proceed?
(I) Set the Partial

Provide an appropriate response.
-If we wish to locate the candidates for local extrema and saddle points in the interior of the domain of a function $f(x, y)$ , then how should we proceed?
(i) Set the partial derivatives equal to each other.
(ii) Set the partial derivatives equal to zero.
(iii) Set the partial derivatives equal to the critical values.

A) Only (iii) is correct.
B) Only (ii) is correct.
C) Only (i) is correct.
D) None of the above is correct.