A bank is trying to determine which model of safe to install. The bank manager believes that each model is equally resistant to safe crackers but sets up a test to be sure. He hires nine safe experts to break into each of the models, timing each endeavor. The results (in seconds) are given next, paired by expert. Let D be the difference: Time to break Safe 1 minus Time to break Safe 2.

Safe 1	Safe 2
103	101
90	94
64	58
110	111
104	103
92	90
145	140
106	110
76	74

Assuming the difference D is normally distributed, which of the following is the 95% confidence interval for D?

Multiple Choice

a) [-1.8677, 3.6455]

b) [-1.6903, 3.6903]

c) [-1.7537, 5.7537]

d) [-0.6739, 4.6738]