If $X$ Is an Exponential Random Variable with the Probability Density Function

Multiple Choice

If $X$ is an exponential random variable with the probability density function $f ( x ) = 23 e ^ { - 23 x } \text { on } [ 0 , \infty ) ,$ find $E ( X )$

A) $46$
B) $23$
C) $\frac { 1 } { 23 }$
D) $\frac { 2 } { 23 }$
E) 1