Find $f ( x )$ If $f ( 8 ) = 24$

Multiple Choice

Find $f ( x )$ if $f ( 8 ) = 24$ and the tangent line at $( x , f ( x ) )$ has slope x. ?

A) $f ( x ) = \frac { x ^ { 2 } } { 2 } - 8$
B) $f ( x ) = \frac { x ^ { 2 } } { 2 } - C$
C) $f ( x ) = - \frac { x ^ { 2 } } { 2 } + 8$
D) $f ( x ) = \frac { x ^ { 2 } } { 2 } + C$
E) $f ( x ) = \frac { x ^ { 2 } } { 2 } + 8$