The probability of an individual touching the outer door and squatting toilet j at time t is not infected, and the probability that he is not infected after touching the outer door at time t1 is:
The probability that the individual is not infected when contacting the outer door and squatting toilet J at time t, and is not infected after contacting the outer door at time T1 is
The probability that an individual is not infected when he touches the outer door and squats in the toilet at time T, and is not infected after he touches the outer door at time t1 is