Answer:
![7\ \text{mm}^2](https://img.qammunity.org/2020/formulas/mathematics/high-school/oa4cp8j0ov3k01s4yheug5tcq2re713zom.png)
Explanation:
Given : A slice is made parallel to the base of a right rectangular pyramid.
The part of the larger rectangle that intersects the pyramid is a smaller gray rectangle.
i.e. the resulting two-dimensional cross-section is represented by smaller gray rectangle.
The front side of the smaller rectangle is labeled 3.5 millimeters, and the right side is labeled 2 millimeters.
Then, the area of the resulting two-dimensional cross-section =
![3.5*2=7\ \text{mm}^2](https://img.qammunity.org/2020/formulas/mathematics/high-school/pvusl36vb81vslc5q9bhha5z0tzhdlrrmg.png)