Unit squares are arranged to form a rectangular grid that is m units wide and n units tall, where m and n are

positive integers with 2n < m < 3n. The region below

one of the diagonals of the rectangle is shaded as shown.

For certain pairs m and n, there is a unit square in the

grid that is not completely shaded but whose shaded area

is greater than 0.999. The smallest possible value of mn

for which this is true satisfies

(A) 496 ≤ mn ≤ 500

(B) 501 ≤ mn ≤ 505

(C) 506 ≤ mn ≤ 510

(D) 511 ≤ mn ≤ 515

(E) 516 ≤ mn ≤ 520