A Random Variable X Is Exponentially Distributed with a Mean $\operatorname { Pr } ( 0 \leq x \leq a ) = 0.75$

Multiple Choice

A random variable X is exponentially distributed with a mean of 10. Determine a so that $\operatorname { Pr } ( 0 \leq x \leq a ) = 0.75$

A) a = ln 0.75
B) a = $\frac { 1 } { 10 }$
C) a = $\frac { 1 } { 10 }$ ln 4
D) a = ln $\frac { 3 } { 4 }$
E) none of these