The doorstop has the shape of a triangular prism.
To compute the Volume of it, first, we need to find the area of the triangle located at the base.
The area of a triangle is calculated as follows:
From the picture, the base is 10 cm and the height is 8 cm, then:
![\begin{gathered} A=10\cdot8\cdot(1)/(2) \\ A=40\operatorname{cm}^2 \end{gathered}]()
Now, we can compute the volume as follows:
![\begin{gathered} V=\text{area of the triangle}\cdot\text{ height of the prism} \\ V=40\cdot3.5 \\ V=140\operatorname{cm}^3 \end{gathered}]()
1 cubic centimeter has a mass of 8.1 grams.
To find the mass of 140 cubic centimeters, we can use the next proportion:
![\begin{gathered} \frac{1\operatorname{cm}}{140\operatorname{cm}^3}=\frac{8.1\text{ grams}}{x\text{ grams}} \\ 1\cdot x=8.1\cdot140 \\ x=1134\text{ grams} \end{gathered}]()