Solve the Equation $$e ^ { 2 x } - 9 e ^ { x } + 20 = 0$$

Multiple Choice

Solve the equation. Give the answer in exact form.
- $$e ^ { 2 x } - 9 e ^ { x } + 20 = 0$$

A) $\left\{ \mathrm { e } ^ { 5 } , \mathrm { e } ^ { 4 } \right\}$
B) $\left\{ \frac { 5 } { \mathrm { e } } , \frac { 4 } { \mathrm { e } } \right\}$
C) $\{ \ln ( - 5 ) , \ln ( - 4 ) \}$
D) $\{ \ln 5 , \ln 4 \}$