Last Year, Nine Employees of an Electronics Company Retired $\begin{array} { l l l } 56 & 65 & 62 \\ 53 & 68 & 58 \end{array}$

Last year, nine employees of an electronics company retired. Their ages at retirement are listed below. Find the mean retirement age. $\begin{array} { l l l } 56 & 65 & 62 \\ 53 & 68 & 58 \end{array}$
$\begin{array} { l l l } 53 & 68 & 58 \end{array}$
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A) $58.2 \mathrm { yr }$
B) $59.4 \mathrm { yr }$
C) $58.8 \mathrm { yr }$
D) $58.0 \mathrm { yr }$