The set S= {AAA,AA,C,D} represents the sizes of batteries a hardware store offers.
The set T= {regular, alkaline, rechargeable} represents the possible types of the batteries. Find the cross product S x T to determine how many different batteries are being sold at the hardware store.
AAA,reg
AAA,alk
...
D,alk
D,rech
4x3 members in SxT