Answer: 9.45%
Step-by-step explanation:
To solve this question, we need to know the weights of securities A and B and this will be:
Weight of A = STD of B / (STD of A + STD of B)
= 40% / (70% + 40%)
= 40% / 110%
= 0.4/1.1
= 0.3636
Weight of security A = 0.3636
Weight of security B = 1 - 0.3636 = 0.6364
Then, the rate of return of risk free portfolio will be:
= (Return of A × Weight of A) + (Return of B × Weight of B)
= (12% × 0.3636) + (8% × 0.6364)
= 0.043632 + 0.050912
= 0.094544
= 9.45%