Task: Question Answering
Input (English): Problem: the two lines y = x and x = - 4 intersect on the coordinate plane . if z represents the area of the figure formed by the intersecting lines and the x - axis , what is the side length r of a cube whose surface area is equal to 6 z ? 
Options: a ) r = 16 , b ) r = 8 √ 2 , c ) r = 8 , d ) r = 2 √ 2 , e ) ( √ 2 ) / 3
Output (English): d