Solve the Formula for the Specified Variable $\frac { 1 } { \mathrm { a } } + \frac { 1 } { \mathrm {~b} } = \frac { 1 } { \mathrm { c } } \quad$

Multiple Choice

Solve the formula for the specified variable.
- $\frac { 1 } { \mathrm { a } } + \frac { 1 } { \mathrm {~b} } = \frac { 1 } { \mathrm { c } } \quad$ for $\mathrm { c }$

A) $c = \frac { a b } { a + b }$
B) $c = \frac { a + b } { a b }$
C) $c = a + b$
D) $c = a b ( a + b )$