ambo mineral water has produced 5000 units during september 1999. standard labor time allowed is 2 hours per unit at $15/hour. during the month 8000 hours have been worked at the total cost of $160,000. variable factory overhead is applied to product on the basis of direct labor hours. it was estimated that $50,000 variable factory overhead would be incurred. actual variable factory overhead turned to be $48,000. what is the budgeted variable overhead rate and the variable factory overhead spending variance?