Producer Behavior $$ End of Chapter Problem

Fast$-$food restaurants like McDonald's are replacing cashiers with touch$-$screen ordering kiosks. Currently, the marginal product of another cashier is $48$ customers served per hour; the marginal product of another kiosk is $32$ customers served per hour. A cashier can be hired for a wage of $$15$; a kiosk rents for $$12.$

a$.$ McDonald's currently minimizing the cost of serving its customers.

b$.$ How might McDonald's improve its profits by changing its input mix?

It couldn't. The marginal product per dollar spent on each input is currently equal.

It could lower its use of both cashiers and kiosks, thereby lowering its costs.

It could replace kiosks with cashiers.

It could replace cashiers with kiosks.