The equation y = -143x3 + 1810x - 187x+2231 where x represents the time in years since January 1, 1983 is a mathematical model for the number of AIDS cases, y, in some population between the years 1983 and 1991. According to this model, how long after January 1, 1983 was the number of AIDS cases in this population 26,488? Round your answer to one decimal place. 4.4 years 4.3 years 4.6 years 4.7 years 5.1 years