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: which is the smallest no which divides 2880 and gives a perfect square ?
Options: ['a ) 4', 'b ) 9', 'c ) 3', 'd ) 5', 'e ) 7']
d

Problem: if the radius of a circle is decreased 20 % , what happens to the area ?
Options: a ) 10 % decrease , b ) 20 % decrease , c ) 36 % decrease , d ) 40 % decrease , e ) 50 % decrease
c

Problem: a certain barrel , which is a right circular cylinder , is filled to capacity with 60 gallons of oil . the first barrel is poured into a second barrel , also a right circular cylinder , which is empty . the second barrel is twice as tall as the first barrel and has twice the diameter of the first barrel . if all of the oil in the first barrel is poured into the second barrel , how much empty capacity , in gallons , is left in the second barrel ?
Options: ['a ) there is no empty capacity', 'b ) 100 gallons', 'c ) 300 gallons', 'd ) 420 gallons', 'e ) 840 gallons']
d