A company making tires for bikes is concerned about the exact width of its cyclocross tires. The company has a lower specification limit of $22\mathrm{.}5$ millimeters and an upper specification limit of $22\mathrm{.}8$ millimeters. The standard deviation is $0\mathrm{.}1$ millimeters and the mean is $22\mathrm{.}6$ millimeters.

What is the process capability index for the process?

Note: Round your answer to $4$ decimal places.