An empty rectangular tank has a capacity of 39 ℓ and a height of 26 cm. At 7 a.m., Tap M is turned on to fill the tank at a rate of 10 ℓ per minute for 20 minutes. After 4 minutes, Tap N is turned on to drain water from the tank at a rate of 5 ℓ per minute for 17 minutes. What is the height of the water level in the tank in the end? Give the answer in 1 decimal place.
1 ℓ = 1000 cm³ 
10 ℓ = 10000 cm³ 
5 ℓ = 5000 cm³ 
39 ℓ = 39000 cm³

Volume of water flowed in from Tap M
= 20 x 10000
= 200000 cm³

Volume of water from drained from Tap N
= 17 x 5000
= 85000 cm³

Volume of water left in the tank
= 200000 - 85000
= 115000 cm³

Base area of the tank
= 39000 ÷ 26
= 1500 cm² 

Height of water left in the tank
= 115000 ÷ 1500
≈ 76.7 cm

Answer(s): 76.7 cm