16. Students participate in labor practice at a factory using 3D printing technology to make models. As shown in the figure, the model is the solid obtained by removing the square pyramid $O - E F G H$ from the rectangular prism $A B C D - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ , where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of their respective edges. Given $A B = B C = 6 \mathrm {~cm} , ~ A A _ { 1 } = 4 \mathrm {~cm}$ , and the density of the 3D printing material is $0.9 \mathrm {~g} / \mathrm { cm } ^ { 3 }$ . Disregarding printing waste, the mass of material needed to make this model is $\_\_\_\_$ g. [Figure]
III. Solution Questions: Total 70 points. Solutions should include written explanations, proofs, or calculation steps. Questions 17-21 are required for all students. Questions 22 and 23 are optional; students answer according to requirements.
(A) Required Questions: Total 60 points.
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16. Students participate in labor practice at a factory using 3D printing technology to make models. As shown in the figure, the model is the solid obtained by removing the square pyramid $O - E F G H$ from the rectangular prism $A B C D - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ , where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of their respective edges. Given $A B = B C = 6 \mathrm {~cm} , ~ A A _ { 1 } = 4 \mathrm {~cm}$ , and the density of the 3D printing material is $0.9 \mathrm {~g} / \mathrm { cm } ^ { 3 }$ . Disregarding printing waste, the mass of material needed to make this model is $\_\_\_\_$ g.\\
\includegraphics[max width=\textwidth, alt={}, center]{35e1ed43-6f5c-4d51-99b3-11f2215f3817-04_378_479_1265_762}
\section*{III. Solution Questions: Total 70 points. Solutions should include written explanations, proofs, or calculation steps. Questions 17-21 are required for all students. Questions 22 and 23 are optional; students answer according to requirements.}
(A) Required Questions: Total 60 points.\\