The mean of five observations is 4 and their variance is 5.2 . If three of these observations are 1, 2 and 6, then the other two observations are

The mean of the numbers $$a, b, 8,5,10$$ is 6 and the variance is 6.80 , then which of the following gives possible values of $$a$$ & $$b$$

Consider the first 10 natural numbers. If we multiply each number by $$-$$1 and add 1 to each number, the variance of the numbers so obtained is