The car door hinge manufacturer is looking to improve the reliability of their products. Their engineers have calculated that their new and improved door hinges should be more reliable and have an increased number of open-close cycles before failure. The number of cycles before failure is expected to follow a normal distribution as follows:

X ~ N (10 500, 810 000)

A.) Calculate the percent of car door hinges with a working life between 9000 and 11 000 cycles.

B.) Calculate how many open-close cycles it would take for a car door hinge to be in the 89th percentile.