Perform the Indicated Operation and Write Your Answer with Positive $\frac { m ^ { - 1 } - n ^ { - 1 } } { ( m n ) ^ { - 1 } }$

Multiple Choice

Perform the indicated operation and write your answer with positive integer exponents.
- $\frac { m ^ { - 1 } - n ^ { - 1 } } { ( m n ) ^ { - 1 } }$

A) $n - m$
B) $m - n$
C) $- \mathrm { n } - \mathrm { m }$
D) $m + n$ m