The number of cars Olivia makes is the input and the number of wheels she uses is the output. The number of wheels is any multiple of 4 up to 28. If she uses 28 wheels, then she makes 7 cars. So the domain is $\displaystyle{\left\lbrace{1},{2},{3},{4},{5},{6},{7}\right\rbrace}\usepackage{cmbright}\Huge\$ and the range is $\displaystyle{\left\lbrace{4},{8},{12},{16},{20},{24},{28}\right\rbrace}\usepackage{cmbright}\Huge\$ .