4. Robbie Wallace is an inspector who earns a base salary of $4,800 per month plus a piece rate of 40 cents per bundle inspected. His company accounts for inspection costs as manufacturing overhead. Because of a payroll department error in June, Robbie was paid $3,600 plus a piece rate of 60 cents per bundle. He received gross wages totaling $5,040. Hint: Robbie's compensation has both paid $3,600 plus a piece rate of 60 cents per bundle. He received gross wages totaling $5,040. Hint: Robbie's compensation has both fixed and variable components. Effect on variable overhead spending variance $ Effect on fixed overhead budget variance \$