Computing labor rate and efficiency variances. The standard labor cost for a unit of product is 3 hours of labor at $7.20 per hour. Compute the labor rate variance and the labor efficiency variance for the month of April 19X2, when 2,000 units were produced in each of the following assumed cases. Show whether the variances are favorable or unfavorable.

a. 5,800 hours of labor were required at a total cost of $42,050.

b. 5,800 hours of labor were required at a total cost of $41,644.

c. 6,108 hours of labor were required at a total cost of $43,977.60.

d. 6,108 hours of labor were required at a total cost of $44,771.64.