Company A holds shares of A, B and C. In the securities portfolio composed of the above-mentioned stocks, the proportion of each stock is 50%, 30% and 20% respectively, and the β coefficient is 2.0, 1.0 and 0.5 respectively. The market yield is 15% and the risk-free yield is 10%. A shares, currently trading at $12 A share, just received A cash dividend of $1.2 A share for the previous year, which is expected to grow by 8% A year after that.

 (1) Calculate the following indicators:

① The beta coefficient of A company's securities portfolio

② Return on Risk (RP) of Company A's securities portfolio;

③ Necessary return rate of A company's securities portfolio (K).

④ the necessary investment rate of return on A stock. (2002)

(2) Use the stock valuation model to analyze whether the current sale of A shares is beneficial to Company A.