Marshfield Tax Company considers 8,000 direct labor hours or 400 tax returns its normal monthly capacity. Its standard variable overhead rate is \($4\) per direct labor hour. During the current month, \($31,500\) of variable overhead cost was incurred in working 7,500 direct labor hours to produce 360 units of product. Determine the following variances, and indicate whether each is favorable or unfavorable:

a. Variable overhead spending

b. Variable overhead efficiency