Lisa is planning to invest in the T-bills and the Vanguard S&P 500 index fund. The T-bill rate is 2.0%. The Vanguard fund has an expected return of 12% and a standard deviation of 20%. Assume Lisas risk aversion coefficient A is 5. According to our asset allocation model, _________ of her optimal complete portfolio should be invested in the Vanguard fund.

50%

20%

75%

100%