Problem: a cube of edge 15 cm is imersed completely in a rectangular vessel containing water . if the dimensions of the base of vessel are 20 cm * 15 cm , find the rise in waer level . 
Options: ['a ) 11.25 cm .', 'b ) 12.25 cm', 'c ) 13.25 cm', 'd ) 14.25 cm', 'e ) none of these']
a