What is the variable manufacturing overhead static-budget variance given the following Information? Actual output units produced Actual machine-hours used 28,000 units 10,000 hours Actual variable manufacturing overhead costs $300,000 Budgeted variable manufacturing overhead costs Budgeted output units 25,000 units $250,000 a) $50,000 unfavourable b) $20,000 unfavourable c) $20,000 favourable d) $50,000 favourable