Please explain why option D

Sussex Company uses a standard cost system and prepared the following budget for May when 24,000 machine hours, cost driver, were planned: variable overhead, $48,000; fixed overhead: $240,000. Actual data for May are below. The variable- overhead spending and efficiency variances, respectively, are Machine hours allowed: 25,000 Machine hours worked: 24.000 Variable overhead incurred: $50,000 Fixed overhead incurred: $250,000 $2,000 F $2,000 U $0 $2,000 U $2,000 U $0 $0 $0 $2,000 U $2,000 F