XYZ Corporation prepares a flexible budget based on production levels. The budgeted variable overhead rate is $5 per direct labor hour, and the budgeted fixed overhead is $20,000 per month. In a month where 1,000 direct labor hours were worked, actual variable overhead costs were $4,500, and actual fixed overhead costs were $21,000. Calculate the variable overhead spending variance, variable overhead efficiency variance, fixed overhead spending variance, and fixed overhead volume variance.

Company ABC produces electronic gadgets. The selling price per unit is $100, and the variable cost per unit is $40. The company has a bottleneck in the production process that limits production to 5,000 units per month. If the company's throughput contribution margin per unit is $30, calculate the throughput accounting operating income for the month.