The figure, not drawn to scale, shows an empty tank measuring 20 cm by 20 cm by 15 cm. Water flows from Tap Q at a rate of 500 mℓ per minute and from Tap R at a rate of 130 mℓ per minute. Tower S and Tower T have a base area of 40 cm² and 60 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 17 minutes.
Volume of the tank
= 20 x 20 x 15
= 6000 cm³ 

Volume of water flow per minute
= 500 + 130 - 120
= 510 cm³/min

Volume of water flow in 17 minutes
= 17 x 510
= 8670 cm³ 

Volume of water in the 2 towers
= 8670 - 6000
= 2670 cm³ 

Total combined base areas of 2 towers
= 40 + 60
= 100 cm² 

Height of water in 2 towers
= 2670 ÷ 100
= 26.7 cm

Total height of water
= 26.7 + 15
= 41.7 cm

Answer(s): 41.7 cm