You hold a diversified $100,000 portfolio consisting of 20 stocks with $5,000 invested in each. The portfolio's beta is 1.12. You plan to sell a stock with b = 0.90 and use the proceeds to buy a new stock with b = 1.80. What will the portfolio's new beta be?
a. 1.286
b. 1.255
c. 1.224
d. 1.194
e. 1.165