Hi, I am working through the below question to improve my understanding. It's very similar to this question 5 but a little different. Could you please provide me with the solution?

I am confused where the (1.96) comes from in the solution provided and the meaning of z = 1/96?

Thanks

"In order to test the durability of as new paint, a highway department has test strips painted across heavily travelled roads in eight dierent locations. If, on the average, the test strips disappear after they had been crossed by 168,479 cars and the standard deviation is 12,851 cars construct a .99 condence interval for the number of cars it will actually take on average to wear o the paint.Also determine a .95 condence interval for the standard deviation of the population."