C&A Chips' potato chip filling process has a lower specification limit of $4\mathrm{.}5$ oz$.$ and an upper specification limit of $5\mathrm{.}5$ oz$.$ The standard deviation is $0\mathrm{.}3$ oz$.$ and the mean is $5$ oz$.$ What is the process capability index for the chip filling process?

Multiple Choice

$3\mathrm{.}33$

$0\mathrm{.}28$

$1\mathrm{.}67$

$0\mathrm{.}56$