What is the covariance and co-efficient of correlation

Question

Stocks L and M have yielded the following returns for the past two years.

Years              Return %
                     L              M
1995             12            14
1996             18            12

(i) What is the expected return on portfolio made up of 60 percent of L and 40 percent of M? Find out the standard deviation of each stock.

(ii) What is the covariance and co-efficient of correlation between stock L and M?

(iii) What is the portfolio risk of a portfolio made up of 60 percent of land 40 percent