Find the Slope of the Tangent Line to the Given $a$

Multiple Choice

Find the slope of the tangent line to the given polar curve at the point specified by the value of $a$ . $r = \frac { 1 } { a } , a = \pi$

A) $- \pi$
B) $\frac { 3 } { \pi }$
C) $- 2 \pi$
D) $\frac { 1 } { 4 }$
E) 3