The tolerance limits for a manufacturing process are LSL $=\mathrm{.}11$mm & USL $=\mathrm{.}25$ mm$.$

The Nominal Value is $\mathrm{.}18$ mm$.$ Find the Sigma Level if $\mathrm{.}06$ is the process standard deviation.

Assume that the process remains centered in the tolerance range.

Assume that the process mean does not drift too much