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Solution:
Employees salaries=50, 55, 60, 65, 70, 72, 75, 80, 84, 89.
\sigma = \left [ \sqrt{\frac{\sum (x_{i} - \mu)^{2}}{N}} \right ]
Mean(\mu)=\frac{50+55+60+65+70+72+75+80+84+89}{10}
Mean(\mu)=70
\sigma=\sqrt{\frac{1}{10}(20^{2}+15^{2}+10^{2}+5^{2}+0+2^{2}+5^{2}+10^{2}+14^{2}+19^{2})}
\sigma=\sqrt{\frac{1}{10}(400+225+100+25+0+4+25+100+196+361)
\sigma=\sqrt{\frac{1436}{10}}
\sigma=\sqrt{143.6}
\sigma=11.983