Suppose that risk-free saving is available at rate rf=1%. There is a risky asset (asset A) with expected return A=8% and risk A=10%. You have initial wealth of $500. Unless otherwise noted, you can also borrow money from the bank at rf. For this question, assume that your initial margin must be higher than 90% when you borrow money. Which one of the following combinations of return and risk (SD) you CANNOT obtain by adjusting portfolio weights? d. (10.1%,13%) b. (8.4%,10.5%) a. (1.70%,1.0%) c. (3.10%,3.0%)