An aquarium is filled with water. The lateral wall of the aquarium is 40 cm long and 30 cm high. Using 10 m/s² for the acceleration due to gravity, and 1 g/cm³ for the density of water, the force on the lateral wall of the aquarium is:
(a) 36 N;
(b) 90 N;
(c) 180 N;
(d) 1500 N.