A student makes a model transformer as shown in the diagram.

Which of the following gives the correct type of transformer and its output voltage?
step-down, 12 V12\text{ V}12 V
step-down, 108 V108\text{ V}108 V
step-up, 12 V12\text{ V}12 V
step-up, 108 V108\text{ V}108 V