Question 1103877
If there is a probability of a floodgate's failing of 0.04, and they are independent,the probability of all 4 failing is 0.04^4=2.56 x 10^(-6), which is less than 0.0005.
The wording for the first part of the question is not clear.  If 1 is out of order, it doesn't affect 2 and 3, and their joint probability of being out of order is 0.04^2=0.0016. The probability the three are out of order is 0.04^3=0.000064.