Problem: a cylindrical cube of radius 12 cm contains water upto a depth of 20 cm . a spherical iron ball is dropped into the tub and thus the level of water is raised by 6.75 cm . the radius of the ball is : 
Options: ['a ) 7 cm', 'b ) 8.5 cm', 'c ) 9 cm', 'd ) 9.5 cm', 'e ) none']
c