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 the base of cone is 3 cm and height is 4 cm . find the volume of the cone ? 
Options: ['a ) 12', 'b ) 75', 'c ) 97', 'd ) 15', 'e ) 91']

Ex Output:
a


Ex Input:
Problem: the length of a rectangle is increased by 40 % while its width is halved . what is the % change in area ? 
Options: ['a ) 25 %', 'b ) 30 %', 'c ) 50 %', 'd ) 65 %', 'e ) 70 %']

Ex Output:
b


Ex Input:
Problem: the perimeter of one face of a cube is 20 cm . its volume will be : 
Options: a ) 125 cm 3 , b ) 400 cm 3 , c ) 250 cm 3 , d ) 625 cm 3 , e ) none of these

Ex Output:

a