can you find b and k

In 1997, 500 runners entered a marathon in Joppetown U.S.A. In 2000, 22,500 runners entered the race. Because of the limited number of facilities, the carrying capacity for the number of racers is C 55,000. The number of racers at any time, t, in years, can be modeled by the logistic function P(t) = - . Complete parts a) through d) below. 1 + Bekt a) What is the value of C? C = 55000 b) Find B. B=L