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: in the xy - plane , a triangle has vertices ( 0,0 ) , ( 4,0 ) and ( 4,6 ) . if a point ( a , b ) is selected at random from the triangular region , what is the probability that a - b > 0 ? 
Options: a ) 1 / 5 , b ) 1 / 3 , c ) 1 / 2 , d ) 2 / 3 , e ) 4 / 5
d

Problem: anup manages to draw 7 circles of equal radii with their centres on the diagonal of a square such that two extreme circles touch two sides of the square and each middle circle touches two circles on either side . find the ratio of radius of the circles to the side of the square . 
Options: ['a ) 1 : ( 2 + 6 ^ ( 1 / 2 ) )', 'b ) 1 : ( 4 + 7 ^ ( 1 / 3 ) )', 'c ) ( 2 + 7 ^ ( 1 / 2 ) ) : 1', 'd ) ( 2 + 7 ^ ( 1 / 2 ) ) : 2', 'e ) none of these']
e

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 %']

b