$7.$ An incentive plan employing a kicker is in use. Below standard performance the worker is guaranteed a rate of $ $6/$ h$,$ and above standard performance the worker is paid $ $9\mathrm{.}20/$ h$.$ A job is studied and a rate of $0\mathrm{.}036$h per piece is set. What is the direct labor cost per piece at the following efficiencies? a$.50$ percent b$.80$ percent c$.98$ percent d$.105$ percent e$.150$ percent