mework L05 M10-21. Variable Overhead Variances Sony (SNE) Assume that the best cost driver that Sony has for variable factory overhead in the assembly depart- ment is machine hours. During April, the company budgeted 720,000 machine hours and $6,480,000 for its Texas plant's assembly department. The actual variable overhead incurred was $6,870,000, which was related to 750,000 machine hours. IBC Required a. Determine the variable overhead spending variance. b. Determine the variable overhead efficiency variance