Albert, Inc. uses flexible budgets. At normal capacity of $16,000$ units, budgeted manufacturing overhead is $$128,000$ variable and $$360,000$ fixed. If Albert had actual overhead costs of $$500,000$ for $18,000$ units produced, what is the difference between actual and budgeted costs?

a$.$ $$4,000$ unfavorable

b$.$ $$4,000$ favorable

c$.$ $$12,000$ unfavorable

d$.$ $$16,000$ favorable