The following labor standards have been established for a particular product: Standard labor hours per unit of output Standard labor rate 4.2 hours $ 20.00 per hour The following data pertain to operations concerning the product for the last month: Actual hours worked Actual total labor cost Actual output 6,800 hours $ 136,680 1,600 units Required: a. What is the labor rate variance for the month? b. What is the labor efficiency variance for the month? (Indicate the effect of each variance by selecting "F" for favorable, "U" for unfavorable, and "None" for no effect (i.e., zero variance). Input all amounts as positive values.) a. Labor rate variance b. Labor efficiency variance