Find the Indicated Maxima or Minima $f(x, y)=4 x y$ , Subject To

Multiple Choice

Find the indicated maxima or minima.
-Maximum of $f(x, y) =4 x y$ , subject to $\mathrm{x}+\mathrm{y}=8$

A) 64 when $x=3, y=5$
B) 64 when $x=4, y=4$
C) 72 when $x=0, y=8$
D) 72 when $x=2, y=6$