Blossom Company's overhead rate was based on estimates of $$189,600$ for overhead costs and $18,960$ direct labour hours. Blossom's standards allow $2$ hours of direct labour per unit produced. Production in May was $840$ units, and actual overhead incurred in May was $$19,000.$ The overhead budgeted for $1,680$ standard direct labour hours is $$16,500($ $$4,740$ fixed and $$11,760$ variable$).$

$($a$)$ Calculate the total, budget, and volume variances for overhead.