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: rectangular floors x and y have equal area . if floor x is 10 feet by 18 feet and floor y is 9 feet wide , what is the length of floor y , in feet ? 
Options: ['a ) 13 1 / 2', 'b ) 20', 'c ) 18 3 / 4', 'd ) 21', 'e ) 24']
b

Problem: the measure of the side of a square is multiplied by 7 . if x represents the perimeter of the original square , what is the value of the new perimeter ? 
Options: a ) 3 x , b ) 4 x , c ) 7 x , d ) 12 x , e ) 27 x
c

Problem: if the length of the longest chord of a certain circle is 10 , what is the radius of that certain circle ? 
Options: ['a ) 2.5', 'b ) 5', 'c ) 10', 'd ) 15', 'e ) 20']

b