The standar time is to established for a manual work cycle by direct time study. The observed time for the cycle averaged $4\mathrm{.}80$ min. The workers performance was rated at $90\%$ on all cycles observed. After eight cycles, the worker must exchange parts containers, which took $1\mathrm{.}60$ min, rated at $120\%.$ The PFD allowance for this class of work is $15\%.$ Determine c$)$ the workers efficiency if the worker produces $123$ work units during an $8$ hour shift