The standards for the new Galaxy phone specify $4\mathrm{.}1$ direct labor$-$hours per unit at $$12\mathrm{.}10$ per direct labor$-$hour. Last month $1,600$ units of the new Galaxy phone were produced using $6,600$ direct labor$-$hours at a total direct labor wage cost of $$77,220.$

Required:

a$.$ What was the labor rate variance for the month?

b$.$ What was the labor efficiency variance for the month?