Suppose the Time X a Customer Must Spend Waiting in Line

question 7

Multiple Choice

Suppose the time X a customer must spend waiting in line at a certain fast food restaurant is a random variable that is exponentially distributed with a density function $f ( x ) = \left\{ \begin{array} { l l } \frac { 1 } { 3 } e ^ { - x / 3 } & \text { if } x \geq 0 \\0 & \text { if } x < 0\end{array} \right.$ where x is the number of minutes that a randomly selected customer spends waiting in line.Find the expected waiting time for customers at the restaurant.

• A)6 minutes
• B)2.5 minutes
• C)3 minutes
• D)1.5 minutes

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