&B Co. provides house cleaning services. The company uses the number of jobs to measure activity. At the beginning of April, the company budgeted for 80 jobs, but the actual number of jobs turned out to be 90. A report comparing the budgeted revenues and costs to the actual revenues and costs appears below: A&B Co. For the Month Ended April 30 Revenue/Cost Formulas Actual Results Planning Budget Number of jobs (Q) 90 80 Revenue $100Q 8,900 8,000 Expenses: Variable expenses ? 3,800 3,200 Fixed expense ? 2,100 2,500 Total expenses 5,900 5,700 Net operating income 3,000 2,300 What is the amount of activity variance for variable expenses in A&Bs performance report for April? A. $600 unfavorable B. $600 favorable C. $400 unfavorable D. $400 favorable