$($c$)$ Naproxen is a nonsteroidal anti$-$inflammatory drug $($NSAID$)$ that is supplied as a single enantiomer. The specific rotation of clinical grade naproxen is $+66.$

The experimentally determined specific rotation of a batch prepared in the development laboratory using an alternative synthesis route is $+62\mathrm{.}3.$

$($i$)$ Determine the optical purity and enantiomeric excess for this batch.

$($ii$)$ Use these values to calculate the percentage of the $(+)$ and $(-)$ enantiomer present in the laboratory sample. Show clearly how you reached your answers.