The investor has a portfolio of five companies with a current market value of 1.5 million PLN. The value of the first two companies is 300000 PLN each. The share of the next two companies is also equal and they constitute 50% of the portfolio (in total). The beta coefficients of these companies are: 1.2; 0.8; -0.3; 1.45; 0.5. The risk of investing in the wide stock exchange index on this market is 20%, while the risk associated with investing in the investor portfolio is estimated to be 18%. a) Describe shortly what is "beta" parameter and how it can be used in finance? b) Is the investor's portfolio a defensive or aggressive portfolio? Explain your answer. c) Which type of risk prevails in the investor's portfolio (diversifiable or non- diversifiable)? Provide calculations and explain