ABC Corporation has a standard costing system in which variable manufacturing overhead is assigned to production on the basis of standard machine-hours. The following data are available for July: Actual variable manufacturing overhead cost incurred: $31,230 Actual machine-hours worked: 1,800 hours Variable overhead rate variance: $4,230 Unfavorable Total variable overhead spending variance: $6,240 Unfavorable The standard number of machine-hours allowed for July production is: a) 2,722 hours b) 1,700 hours Incorrect c) 1,666 hours d) 1,500 hours