Problem: a sixth grade teacher asked her students to draw rectangles with positive integer length and a perimeter of 42 . the difference between the largest and smallest possible ares of the rectangles that the students could have come up with is ? 
Options: ['a ) 50 sq units', 'b ) 60 sq units', 'c ) 70 sq units', 'd ) 80 sq units', 'e ) 90 sq units']
e