A metallic cube of side 10 cm, density 6.8 gm/cc is floating in liquid mercury (density 13.6gm/cc), with 5 cm height of cube exposed above the mercury level. Water (density 1 gm/cc) is filled over this, to submerge the cube fully. The new height of cube exposed above mercury level is

A

4.6 cm

B

5.4 cm

C

5.0 cm

D

5.8 cm