On 1 January, Hellen's portfolio is valued at $1000000. Hellen want to make a $100000 payment to buy a house on 31 December of the same year, but does not want the year-end portfolio value to fall below $1000000. The expected annual return on the investor's existing portfolio is 15 percent with an expected standards deviation of 20 percent. The risk-free rate is 8%. The safety-first ratio for the portfolio is closest to（     ）。