Answer: 8
Explanation:
Expressing the value of A that would equate the risk-free rate to the risky portfolio is;
0.06 = 0.15 − A/2(0.15)²
0.06 - 0.15 = -0.01125 * A
A = (0.06 - 0.15) / -0.01125
A = 8
With A being 8, the investor would be indifferent between the risk free asset and the risky portfolio according to their utility function.