Answer:
Of the following factors, the manufacturer's production volume variance is most likely to have been caused by: 
D. Temporary employment of workers with lower skill levels than originally anticipated.
Explanation:
a) Data and Calculations:
Estimated practical capacity = 90,000 machine hours
Machine hours per unit = 2
Estimated production units based on capacity = 45,000 (90,000/2)
                                                    Budgeted          Actual
Variable overhead =                 $200,000      $240,000
Actual fixed overhead =           $450,000      $442,000
Machine hours                             90,000           88,000
Units produced                            45,000           42,000
Estimated units to be produced based on standard machine hour
= 44,000 units (88,000/2)
Variance between standard units to be produced and actual = 2,000 (44,000 - 42,000) Unfavorable