Beaver Corporation is an oil well service company that measures its output by the number of wells serviced. The company has provided the following fixed and variable cost estimates that it uses for budgeting purposes. Fixed element Variable Element per per month Well Serviced Revenue $ 4,500 Employee salaries and wages $ 57,200 $ 1,100 Servicing materials $ 600 Other expenses $ 31,000 The planning budget for May was based on 36 wells serviced, but a total of 31 wells were actually serviced in May. The activity variance for "Employee salaries and wages" for May would have been closest to