Which of the following are aromatic?

Give plausible explanation for:
(a) Diazonium salts of aromatic amines are stable.
(b) Aniline does not undergo Friedel-Crafts reaction.
(c) Aniline on nitration gives substantial meta product.
For a statistical data \( x_1, x_2, \dots, x_{10} \) of 10 values, a student obtained the mean as 5.5 and \[ \sum_{i=1}^{10} x_i^2 = 371. \] He later found that he had noted two values in the data incorrectly as 4 and 5, instead of the correct values 6 and 8, respectively.
The variance of the corrected data is: