The figure shows a container made up of 3 sections. Cuboid C with a square base of side 14 cm and height 42 cm. Cube D with a side of 10 cm. Cuboid E that is 72 cm by 30 cm by 50 cm. Water from a tap above flows down at a rate of 3.7 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 67 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of D
= 10 x 10 x 10
= 1000 cm³ 

Volume of E
= 72 x 30 x 50
= 108000 cm³ 

2 ℓ = 2000 cm³ 
3.7 ℓ = 3700 cm³ 

Net increase in volume per minute
= 3700 - 2000
= 1700 cm³/min

Height of C to be filled with water
= 67 - (50 + 10)
= 7 cm

Volume of water in C
= 14 x 14 x 7
= 1372 cm³ 

Volume of water in E, D and part of C
= 108000 + 1000 + 1372
= 110372 cm³ 

Time taken to reach height
= 110372 ÷ 1700
≈ 65 min (Correct to nearest whole number)

Answer(s): 65 min