Answer:
[tex]V=144\ cm^3[/tex]
Step-by-step explanation:
#We use the base diagonal and the height diagonal to calculate the beam's height:
[tex]h=\sqrt{13^2-(4^2+3^2)}\\\\h=12\ cm[/tex]
#The volume of the beam can then be calculated as:
[tex]V=lwh\\\\=4\times 3\times 12\\\\=144\ cm^3[/tex]
Hence, the beam's volume is [tex]144\ cm^3[/tex]
