Three cubes of metal whose edges are 3 cm, 4 cm and 5 cm are melted to form a bigger cube. If there is no loss of metal in this process, then the diagonal of the bigger cube, in centimeters, is
1
\(3\sqrt 3\)
2
\(4 \sqrt 3 \)
3
\(8 \sqrt 3 \)
4
\(6 \sqrt 3 \)