In r programming

In a study on cholesterol levels a sample of 12 men was chosen. The plasma cholesterol levels (mmol/L) of the subjects were as follows:

6.0, 6.4, 7.0, 5.8, 6.0, 5.8, 5.9, 6.7, 7.1, 6.5, 6.3, 5.8

(a) Estimate the variance of the plasma cholesterol levels with a 99% confidence interval.

(b) What assumptions did you make about the sample in order to make your estimate?