Isabel invested in a four-stock portfolio; she invested 20 percent of her money in Stock A, 30 percent of her money in Stock B, 25 percent of her money in Stock C, and 25 percent of her money in Stock D. The betas for Stock A, B, C, and D are 0.4, 1.2, 2.5, and 1.75, respectively, and their expected returns are 12 percent, 24 percent, 30 percent, and 28 percent, respectively. What is the beta of Isabel's portfolio?

a. 1.82

b. 1.38

c. 1.50

d. 1.43

e. 1.96