The figure, not drawn to scale, shows an empty tank measuring 20 cm by 20 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 180 mℓ per minute. Tower M and Tower N have a base area of 60 cm² and 70 cm² respectively. Water is drained out of the container at a rate of 140 mℓ per minute. Find the height of the water level after 19 minutes.
Volume of the tank
= 20 x 20 x 25
= 10000 cm³ 

Volume of water flow per minute
= 500 + 180 - 140
= 540 cm³/min

Volume of water flow in 19 minutes
= 19 x 540
= 10260 cm³ 

Volume of water in the 2 towers
= 10260 - 10000
= 260 cm³ 

Total combined base areas of 2 towers
= 60 + 70
= 130 cm² 

Height of water in 2 towers
= 260 ÷ 130
= 2 cm

Total height of water
= 2 + 25
= 27 cm

Answer(s): 27 cm