5 or 6 pounds because there not that heavy
The dimensions of the carton are:
10 x 10 x 10 [inch OR unit cubes - it's the same since cubes' dimensions are 1 x 1 x 1 inch)
I attach the explanation below.
(a) * (a+1) = 420
a^2 + a = 420
a^2 + a - 420 = 0
(a+21)(a-20) = 0
a = -21 OR 20
The two integers can be -21 and -20, OR 20 and 21.