16. Students participate in labor practice at a factory using 3D printing technology to make models. As shown in the figure, the model is a rectangular prism $A B C D - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ with a square pyramid $O - E F G H$ removed, where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of their respective edges. $A B = B C = 6 \mathrm {~cm} , ~ A A _ { 1 } = 4 \mathrm {~cm}$ . 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 questions that all candidates must answer. Questions 22 and 23 are optional questions; candidates 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 a rectangular prism $A B C D - A _ { 1 } B _ { 1 } C _ { 1 } D _ { 1 }$ with a square pyramid $O - E F G H$ removed, where $O$ is the center of the rectangular prism, and $E , F , G , H$ are the midpoints of their respective edges. $A B = B C = 6 \mathrm {~cm} , ~ A A _ { 1 } = 4 \mathrm {~cm}$ . 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.\\
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III. Solution Questions: Total 70 points. Solutions should include written explanations, proofs, or calculation steps. Questions 17--21 are required questions that all candidates must answer. Questions 22 and 23 are optional questions; candidates answer according to requirements.\\
(A) Required Questions: Total 60 points.\\