The figure shows a container made up of 3 sections. Cuboid Z with a square base of side 9 cm and height 46 cm. Cube A with a side of 11 cm. Cuboid B that is 74 cm by 26 cm by 42 cm. Water from a tap above flows down at a rate of 2.6 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 68 cm from the base? Give the answer in minutes correct to nearest whole number.
Volume of A
= 11 x 11 x 11
= 1331 cm³ 

Volume of B
= 74 x 26 x 42
= 80808 cm³ 

2 ℓ = 2000 cm³ 
2.6 ℓ = 2600 cm³ 

Net increase in volume per minute
= 2600 - 2000
= 600 cm³/min

Height of Z to be filled with water
= 68 - (42 + 11)
= 15 cm

Volume of water in Z
= 9 x 9 x 15
= 1215 cm³ 

Volume of water in B, A and part of Z
= 80808 + 1331 + 1215
= 83354 cm³ 

Time taken to reach height
= 83354 ÷ 600
≈ 139 min (Correct to nearest whole number)

Answer(s): 139 min