The standard was based on the planned activity of 9,000 machine hours (3,000 units) ABC has the following overhead standard: Variable overhead: 3 hours at $6 per hour Fixed overhead: 3 hours at $4 per hour Actual data is as follow: Variable overhead costs incurred: $30,000 Fixed overhead costs incurred: $20,000 Machine hours worked: 6,000 MHs Actual units produced: 2,000 units What is ABC's variable overhead spending variance? a. $6000 favorable b. $6000 unfavorable. c. $16,000 favorable d. $16,000 unfavorable