The figure, not drawn to scale, shows an empty container measuring 20 cm by 15 cm by 20 cm. Water flows from Tap K at a rate of 500 mℓ per minute and from Tap L at a rate of 150 mℓ per minute. Tower M and Tower N have a base area of 10 cm² and 40 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 container
= 20 x 15 x 20
= 6000 cm³ 

Volume of water flow per minute
= 500 + 150 - 160
= 490 cm³/min

Volume of water flow in 19 minutes
= 19 x 490
= 9310 cm³ 

Volume of water in the 2 towers
= 9310 - 6000
= 3310 cm³ 

Total combined base areas of 2 towers
= 10 + 40
= 50 cm² 

Height of water in 2 towers
= 3310 ÷ 50
= 66.2 cm

Total height of water
= 66.2 + 20
= 86.2 cm

Answer(s): 86.2 cm