A slice is made parallel to the base of a right rectangular pyramid, as shown
What is the area of the resulting two-dimensional cross-section?
2 mm
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3.5 mm
5 mm
mm
4 mm
7 mm

Oh i'm sorry. didn't see the options

Use pythagorean’s theorem and find the missing side lengths of the two smaller triangles and add them together
13^2 - 12^2 = 5
15^2 - 12^2 = 9
5+9 = 14
14 is the length of each side of the square
14^2 + 14^2 = 19.8
19.8 is the diagonal length of the inside if the square