The figure shows a container made up of 3 sections. Cuboid C with a square base of side 14 cm and height 40 cm. Cube D with a side of 18 cm. Cuboid E that is 64 cm by 11 cm by 43 cm. Water from a tap above flows down at a rate of 3.9 litres per minute while water is drained out from the bottom at a rate of 2 litre per minute. How long did it take to fill up the container to a height of 69 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of D
= 18 x 18 x 18
= 5832 cm³ 

Volume of E
= 64 x 11 x 43
= 30272 cm³ 

2 ℓ = 2000 cm³ 
3.9 ℓ = 3900 cm³ 

Net increase in volume per minute
= 3900 - 2000
= 1900 cm³/min

Height of C to be filled with water
= 69 - (43 + 18)
= 8 cm

Volume of water in C
= 14 x 14 x 8
= 1568 cm³ 

Volume of water in E, D and part of C
= 30272 + 5832 + 1568
= 37672 cm³ 

Time taken to reach height
= 37672 ÷ 1900
≈ 20 min (Correct to nearest whole number)

Answer(s): 20 min