Assume that the best cost driver that Sony has for variable factory overhead in the assembly department is machine hours. During April, the company budgeted 480,000 machine hours and $4,000,000 for its Texas plant's assembly department. The actual variable overhead incurred was $4,180,000, which was related to 500,000 machine hours.

(a) Determine the variable overhead spending variance.

(b) Determine the variable overhead efficiency variance.