Computation of the difference between actual and budgeted costs:-

Variable cost per unit = Budgeted manufacturing overhead / Normal capacity

= $78,000 / 26,000

= $3 per unit

Variable cost at 28,000 units = Variable cost per unit * 28,000

= $3 * 28,000

= $84,000

Budgeted cost at 28,000 Units = Variable cost + Fixed cost

= $84,000 + $270,000

= $354,000

Difference = Actual cost - Budgeted cost

= $348,400 - $354,000

= $5,600 (Favorable)