A temperature regulator is put in the container of some liquid. The temperature of the temperature regulator is fixed at d degree centigrade, the temperature of the liquid x (degree centigrade) is a random variable, and x ~ n (d,0.5²). (1) if d=90, find the probability p (x<89) (2) if the probability that the temperature of the liquid keeps at least 80 (degree centigrade) is required to be more than 0.99, find the minimum d.