The area of a triangle can be calculated using the formula A = 1/2 * base * height.
For the first triangular base:
A = 1/2 * 3cm * 4cm = 6 square cm
For the second triangular base:
A = 1/2 * 4cm * 5cm = 10 square cm
So the total area of the two bases is 6 + 10 = 16 square cm.
The closest option is 12 (B).