Find the Indicated Probability $$\mathrm { f } ( \mathrm { x } ) = \mathrm { e } ^ { - \mathrm { x } ; } ; [ 0 , \infty ) , \mathrm { P } ( \mathrm { x } \geq 7 )$$

Multiple Choice

Find the indicated probability.
- $$\mathrm { f } ( \mathrm { x } ) = \mathrm { e } ^ { - \mathrm { x } ; } ; [ 0 , \infty ) , \mathrm { P } ( \mathrm { x } \geq 7 )$$

A) $0.9991$
B) 0
C) $0.0009$
D) The function $\mathrm { f } ( \mathrm { x } )$ is not a probability density function.