At a certain instant, the length ℓ, width w, and height h of a box are ℓ = 4 m and w = h = 1 m. If ℓ and w are increasing at a rate of 7 m/s, what is the rate of change of volume with respect to time?
a. 7 m³/s
b. 8 m³/s
c. 9 m³/s
d. 10 m³/s