Controller of Simmons Company is in the process of analyzing its manufacturing overhead costs for March. March results follow: Budgeted amounts: Machine hours Variable overhead rate 0.50 hours per unit $15.00 per machine hour Actual amounts for August: Variable overhead incurred $190,000 Machine hours worked 11,000 hours Actual output 20,000 units Budgeted machine hours per unit are used to allocate variable manufacturing overhead. Determine the variable overhead efficiency variance. Select one: o a. $25,000 U O b. $15,000 U O c. $25,000 F O d. $15,000 F