Why is it difficult to evaluate if a project achieved the desired goal or MOV shortly after implementation

Kirnon clinic uses client-visits as its measure of activity. during july, the clinic budgeted for 3,250 client-visits, but its actual level of activity was 3,160 client-visits. the clinic has provided the following data concerning the formulas to be used in its budgeting: fixed element per month variable element per client-visitrevenue - $ 39.10personnel expenses $ 35,100 $ 10.30medical supplies 1,100 7.10occupancy expenses 8,100 1.10administrative expenses 5,100 0.20total expenses $ 49,400 $ 18.70the activity variance for net operating income in july would be closest to: