A cubical solid aluminium (bulk modulus = −V dP/dV = 70 GPa) block has an edge length of 1 m on the surface of the earth. It is kept on the floor of a 5 km deep ocean. Taking the average density of water and the acceleration due to gravity to be 10³ kg m⁻³ and 10 m s⁻², respectively, the change in the edge length of the block in mm is _____.