In this task, you need to answer the given multiple-choice question on geometry. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Ex Input:
Problem: the radius of a sphere is increased by 50 % . the increase in surface area of the sphere is : 
Options: a ) 168 , b ) 125 , c ) 186 , d ) 197 , e ) 191

Ex Output:
b


Ex Input:
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']

Ex Output:
c


Ex Input:
Problem: two equal triangles constitute rhombus a . if the diagonals of rhombus are 15 cm and 20 cm long . what is the area of each triangle ? 
Options: ['a ) 300', 'b ) 150', 'c ) 75', 'd ) 40', 'e ) 20']

Ex Output:

c