A fund manager has a well-diversified portfolio that mirrors the performance of the S&P 500 and is worth $300 million. The value of the S&P 500 is 4,800, and the portfolio manager would like to obtain insurance against a reduction of more than 4% in the value of the portfolio over the next six months. The risk-free interest rate is 5% per annum. The dividend yield on both the portfolio and the S&P 500 is 3%, and the volatility of the index is 25% per annum. What amount (in dollars) of the portfolio should be sold and kept in risk-free securities for portfolio insurance?