Consider the following for the two (02) items that follow:
The sum and the sum of squares of the observations corresponding to length X (in cm) and weight Y (in gm) of 50 tropical tubers are given as $\Sigma X = 200$, \Sigma Y = 250, \Sigma X^2 = 900 and \Sigma Y^2 = 1400$

Which one of the following statements is correct?

The arithmetic mean of 100 observations is 50. If 5 is subtracted from each observation and then divided by 20, then what is the new arithmetic mean?

The standard deviation of 100 observations is 10. If 5 is added to each observation and then divided by 20, then what will be the new standard deviation?

What is the arithmetic mean of 8²,9²,10²,...,15²?