The figure, not drawn to scale, shows an empty container measuring 20 cm by 15 cm by 15 cm. Water flows from Tap Z at a rate of 300 mℓ per minute and from Tap A at a rate of 160 mℓ per minute. Tower B and Tower C have a base area of 50 cm² and 50 cm² respectively. Water is drained out of the container at a rate of 150 mℓ per minute. Find the height of the water level after 15 minutes.
Volume of the container
= 20 x 15 x 15
= 4500 cm³ 

Volume of water flow per minute
= 300 + 160 - 150
= 310 cm³/min

Volume of water flow in 15 minutes
= 15 x 310
= 4650 cm³ 

Volume of water in the 2 towers
= 4650 - 4500
= 150 cm³ 

Total combined base areas of 2 towers
= 50 + 50
= 100 cm² 

Height of water in 2 towers
= 150 ÷ 100
= 1.5 cm

Total height of water
= 1.5 + 15
= 16.5 cm

Answer(s): 16.5 cm