An empty rectangular container has a capacity of 91 ℓ and a height of 14 cm. At 8 a.m., Tap J is turned on to fill the container at a rate of 9 ℓ per minute for 17 minutes. After 2 minutes, Tap K is turned on to drain water from the container at a rate of 3 ℓ per minute for 21 minutes. What is the height of the water level in the container in the end? Give the answer in 1 decimal place.
1 ℓ = 1000 cm³ 
9 ℓ = 9000 cm³ 
3 ℓ = 3000 cm³ 
91 ℓ = 91000 cm³

Volume of water flowed in from Tap J
= 17 x 9000
= 153000 cm³

Volume of water from drained from Tap K
= 21 x 3000
= 63000 cm³

Volume of water left in the container
= 153000 - 63000
= 90000 cm³

Base area of the container
= 91000 ÷ 14
= 6500 cm² 

Height of water left in the container
= 90000 ÷ 6500
≈ 13.8 cm

Answer(s): 13.8 cm