The figure, not drawn to scale, shows an empty container measuring 20 cm by 20 cm by 15 cm. Water flows from Tap T at a rate of 500 mℓ per minute and from Tap U at a rate of 140 mℓ per minute. Tower V and Tower W have a base area of 20 cm² and 20 cm² respectively. Water is drained out of the container at a rate of 120 mℓ per minute. Find the height of the water level after 13 minutes.
Volume of the container
= 20 x 20 x 15
= 6000 cm³ 

Volume of water flow per minute
= 500 + 140 - 120
= 520 cm³/min

Volume of water flow in 13 minutes
= 13 x 520
= 6760 cm³ 

Volume of water in the 2 towers
= 6760 - 6000
= 760 cm³ 

Total combined base areas of 2 towers
= 20 + 20
= 40 cm² 

Height of water in 2 towers
= 760 ÷ 40
= 19 cm

Total height of water
= 19 + 15
= 34 cm

Answer(s): 34 cm