The mean of numbers $a, b, 8,5,10$ is 6 and their variance is 6.80. Then $\operatorname{Tan}^{-1} \frac{1}{a}+\operatorname{Tan}^{-1} \frac{1}{b}=$

• A

  $\operatorname{Tan}^{-1} \frac{7}{12}$
• B

  $\operatorname{Tan}^{-1}\left(-\frac{7}{11}\right)$
• C

  $\operatorname{Tan}^{-1} \frac{11}{7}$
• Correct answer
  D

  $\operatorname{Tan}^{-1} \frac{7}{11}$

Hence, the correct answer is option: 'D'.