Answer:
2.21
Step-by-step explanation:
Portfolio beta = Respective beta*Respective weight
Beta of market=1;Beta of risk-free assets=0
1.28 = (0.25*0) + (0.31*1) + (0.44*Beta of Stock B)
1.28 = 0 + 0.31 + 0.44*Beta of Stock B
1.28 - 0.31 = 0.44*Beta of Stock B
Beta of Stock B = 0.97/0.44
Beta of Stock B = 2.204545454545455
Beta of Stock B = 2.21