A company using Six Sigma methodology is operating at a $99\mathrm{.}99967\%$ defect free rate.

What is its Sigma Level and failure rate

a$.3$ Sigma, $3\mathrm{.}4$ DPMO

b$.4\mathrm{.}5$ Sigma, $233$ DPMO

c$.5\mathrm{.}0$ Sigma, $233$ DPMO

d$.6$ Sigma, $3\mathrm{.}4$ DPMO