A company implements a new process to manufacture its product and uses $100$ hours to complete one unit. It expects that the new process will be subject to an $80\%$ learning curve. If the company assumes the learning curve will follow the cumulative average$-$time learning model, what is the average time needed to produce four batches?

$256$ hours

$60$ hours

$64$ hours

$51\mathrm{.}2$ hours