Let $f ( x , y ) = 5 x - 3 y$

Multiple Choice

Let $f ( x , y ) = 5 x - 3 y$ with constraint $x ^ { 2 } + y ^ { 2 } = 136$ . Then f has a relative minimum at

A) $( 6,10 )$
B) $( 6 , - 10 )$
C) $( - 10,6 )$
D) $( 10,6 )$
E) $( 10 , - 6 )$