$13\mathrm{.}3$ The standard time is to be established for a manual work cycle by direct time study. Theobserved time for the cycle averaged $4\mathrm{.}80$ min. The workers performance was rated at $90\%$ on allcycles 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 $($a$)$ the normal timeand $($b$)$ the standard time for the cycle. $($c$)$ If the worker produces $123$ work units during an $8-$hourshift, what is the workers efficiency?