Answer
Total number of different choices of pens with this brand equals to 12.
Work Step by Step
We know that the situation involves making choices with two groups of items.
We use the Fundamental Counting Principle to find the number of different choices of pens with this brand. Multiply the number of choices for each of the two groups. That is,
$4\times 3=12$
Hence, there are 12 choices of pen with this brand.
