The figure, not drawn to scale, shows an empty tank measuring 20 cm by 15 cm by 20 cm. Water flows from Tap Q at a rate of 400 mℓ per minute and from Tap R at a rate of 230 mℓ per minute. Tower S and Tower T have a base area of 20 cm² and 30 cm² respectively. Water is drained out of the container at a rate of 160 mℓ per minute. Find the height of the water level after 19 minutes.
Volume of the tank
= 20 x 15 x 20
= 6000 cm³ 

Volume of water flow per minute
= 400 + 230 - 160
= 470 cm³/min

Volume of water flow in 19 minutes
= 19 x 470
= 8930 cm³ 

Volume of water in the 2 towers
= 8930 - 6000
= 2930 cm³ 

Total combined base areas of 2 towers
= 20 + 30
= 50 cm² 

Height of water in 2 towers
= 2930 ÷ 50
= 58.6 cm

Total height of water
= 58.6 + 20
= 78.6 cm

Answer(s): 78.6 cm