Lowell Thomas produced $4,000$ units during his $40$ hour workweek. Thomas's regular rate of pay is $$0\mathrm{.}12$ per unit; he is paid an incentive bonus of four cents for each unit produced over $3,000.$ Thomas's overtime rate is

a$.$ $$22\mathrm{.}75$ per hour

b$.$ $$20\mathrm{.}75$ per hour

c$.$ $$13\mathrm{.}00$ per hour

d$.$ $$19\mathrm{.}50$ per hour