1. ChocoCakes sells chocolate brownies and claims they are good value for money.  Sasha, an inspector, takes a random sample of 40 brownies and records the mass, $M$ grams, of each one.  The results are summarised as follows.

$\summ=3404\sum{m}^{2}=297409$

Calculate an unbiased estimate of the population mean of the mass of a brownie and show that an unbiased estimate for the variance is 198 g, correct to 3 significant figures.