The figure, not drawn to scale, shows an empty tank measuring 20 cm by 15 cm by 25 cm. Water flows from Tap K at a rate of 500 mℓ per minute and from Tap L at a rate of 230 mℓ per minute. Tower M and Tower N have a base area of 20 cm² and 80 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 19 minutes.
Volume of the tank
= 20 x 15 x 25
= 7500 cm³ 

Volume of water flow per minute
= 500 + 230 - 120
= 610 cm³/min

Volume of water flow in 19 minutes
= 19 x 610
= 11590 cm³ 

Volume of water in the 2 towers
= 11590 - 7500
= 4090 cm³ 

Total combined base areas of 2 towers
= 20 + 80
= 100 cm² 

Height of water in 2 towers
= 4090 ÷ 100
= 40.9 cm

Total height of water
= 40.9 + 25
= 65.9 cm

Answer(s): 65.9 cm