A local doctor's office is considering purchasing automatic check$-$in kiosks. The kiosks would allow patients to check themselves in when they arrive for an appointment. In addition, the kiosks feature touchscreens allowing patients to e$-$sign required forms. The kiosks would allow the office to reduce staff and labor expenditures while increasing the number of people that receive services at the doctor's office. In this example, the reduction of staff and labor expenditures that result from adding the kiosks represent $\_\_\_\_.$

a$.$ a cost driver

b$.$ a revenue driver

c$.$ differentiation value

d$.$ commodity value