Subtract the Rational Expressions $\frac { n - 4 } { 9 } - \frac { n - 7 } { 12 }$

Multiple Choice

Subtract the rational expressions. Be sure to express your answer in simplest form. $\frac { n - 4 } { 9 } - \frac { n - 7 } { 12 }$

A) $\frac { 3 n + 5 } { 108 }$
B) $\frac { 21 n - 37 } { 108 }$
C) $\frac { n + 5 } { 36 }$
D) $\frac { n - 37 } { 36 }$