Explanation:
a box (like a "deformed" die) has 6 sides.
and in case of such a rectangular box there are 3 pairs of equal sides.
the area of each side is a rectangle.
top and bottom : 19×12 times 2
front and back : 19×3 times 2
left and right : 12×3 times 2
so, we get
19×12×2 + 19×3×2 + 12×3×2 = 642 in²
and now, we need 10% more.
10% = 642/10 = 64.2 in²
the total is then
642 + 64.2 = 706.2 ≈ 706 in²