Explanation:
one funny thing about pyramids is the fact that the volume is always
base area × height / 3
no matter if the top of the pyramid is centered over the middle of the base area or shifted off or even shifted off that much that the top is not even over the base area anymore (like in our example here).
so, the volume is
7² × 8.5 / 3 = 49 × 8.5 / 3 = 138.8333333... in³ ≈
≈ 139 in³