I am trying to understand the solution to the below question. The equation to use is simple, but what do you do with the N ^ -1 that gets us to the solution of 0.915. My calculation doesn't come out to that number

A fund's risk appetite is such that it wants to be 97.5% certain it will not lose more than 25% in any one year. Using the performance of the S&P 500 between 1994 and 2003 (see Table 27.2) determine the beta the fund should have. Assume a risk-free rate of 2.5% per annum.

27.10. A fund's risk appetite is such that it wants to be 97.5% certain it will not lose more than 25% in any one year. Using the performance of the S&P 500 between 1994 and 2003 (see Table 27.2) determine the beta the fund should have. Assume a risk-free rate of 2.5% per annum. In equation (27.1), we set R=-0.25, R = 0.025, Rv = 0.1113, M = 0.1974, and p=0.975. The appropriate beta is -0.25 -0.025 = 0.915 0.1113 -0.025+ N(0.025) x 0.1974