Answer:
[tex]4\sqrt{5}\ un.[/tex]
Step-by-step explanation:
The picture shows rectangular prism with rectangular base and heigth h. The dimenssions of base rectangle are l and w.
The diagonal of reactangle with known length l and width w can be calculated using the Pythagorean theorem:
[tex]d^2=l^2+w^2,\\ \\d^2=8^2+4^2,\\ \\d^2=64+16,\\ \\d^2=80,\\ \\d=4\sqrt{5}\ un.[/tex]
