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 cylinder is 2 r units and height is 3 r units . find the curved surface ?
Options: a ) 18 r 2 , b ) 12 r 2 , c ) 3 r 2 , d ) 6 r 2 , e ) 9 r 2

Ex Output:
b

Ex Input:
Problem: the ratio between the perimeter and the width of a rectangle is 5 : 1 . if the area of the rectangle is 294 sq . cm , what is the length of the rectangle ?
Options: a ) 15 cm , b ) 18 cm , c ) 21 cm , d ) 24 cm , e ) 27 cm

Ex Output:
c

Ex Input:
Problem: the water level in a rectangular swimming pool measuring 40 feet by 25 feet is to be lowered by 6 inches . how many gallons of water must be removed ? ( 1 cu ft = 7.5 gallons )
Options: a ) 100 , b ) 250 , c ) 750 , d ) 3750 , e ) 5625

Ex Output:
d