4. an investor currently holds the following portfolio. 8,000 shares of stock a, worth $16,000; beta =1.3. 15,000 shares of stock b, worth $47,000; beta =2. 25,000 shares of stock c , worth $97,000; beta =2.3 the investor is worried that her portfolio beta is too high so she wants to sell some stock c and add stock d , which has a beta of 0.9 to the portfolio. if the investor wants her portfolio to have a beta of 1.72 , how much of stock c should she replace with stock d?