9. The weight of the crate follows a normal distribution , and the crate is hoisted using ropes AB and AC with a constant speed. AB always remains horizontal, and is . If the strength (maximum tension) of the ropes also follows a normal distribution and S is independent of W, determine the probability that rope AB and AC will break, respectively.

Solution: The probability of the break of rope AC is 0.259 and the probability of the break of rope AB is 0.097.