Relevant cost question from BPP revision kit

Hi, I have doubts about the answer to the following question from BPP revision kit. It seems to me that relevant cost for material X is not correct.
Shouldn’t it be 300×3+200×7=2300? If not, what is the correct relevant cost for material X?

The following information is available for identifying the relevant cost of materials for a job for a customer.
The company’s management wants to establish a minimum price at which it is prepared to take on the job.
Material Total quantity Currently in Carrying value Realisable value Replacement
required inventory per kg per kg cost per kg
kg kg $ $ $
W 500 0 – – 8
X 500 300 5 3 7
Y 500 400 8 9 11
Z 100 100 10 12 15
Material Y is in regular use by the company. Materials X and Z are no longer in regular use. There is no alternative use for Material X but the 100 kg of Material Z could be used instead of 150 kg of Material V on a different job. Material V costs $9 per kg and there is currently none of this material in inventory.
What is the relevant cost of these materials for the job under consideration?
A $10,850
B $11,350
C $12,200
D $12,350

Answer by BPP $
Material W 500 kg × $8 4000
Material X 500 kg x $3 1500
Material Z 500 kg x $11 5500
Material Z Higher of (100 x $12)
and (150 x $9) 1350

Total 12350