Treasury bills are paying a 4% rate of return. A risk-averse investor with a risk aversion of A = 3 should invest entirely in a risky portfolio with a standard deviation of 24% only if the risky portfolio's expected return is at least ______.
A. 8.67%
B. 9.84%
C. 21.28%
D. 14.68%
Answer: C. 21.28%