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

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

Problem: the side of a square has the length of 6 . what is the area of the region shaded ? 
Options: ['a ) 48 - 8 π', 'b ) 48 - 6 π', 'c ) 24 + 6 π', 'd ) 16 + 8 π', 'e ) 64 - 8 π']
b

Problem: if two sides of a triangle are 6 and 13 , respectively , which of the following could not be the area of this triangle ? 
Options: ['a ) 40', 'b ) 6', 'c ) 17', 'd ) 29', 'e ) 38']

a