consolidated

Parket Co Suket Co
$’000 $’000
Cost of sales 710 480
Parket Co consistently made sales of $20,000 per month to Suket Co throughout the year. At the year end, Suket Co held $20,000 of this in inventory. Parket Co made a mark-up on cost of 25% on all sales to Suket Co.
What is Parket Co’s consolidated cost of sales for the year ended 31 March 20X7?

The answer:
710,000 + (480,000 x 3/12) – (20,000 x 3) + (20,000 x 25/125) = $774,000

why dont we use the cost of sale of (480*80%*3/12) and instead just (480*3/12), one of the things that confuses me the most is consolidate question, because idk whether do i need to include 100% of the company that we bought, or just the percentage of it ie 80%, can you please help me on this, maybe u can like make it simpler for me to understand, my exam is in 15 hour so rip, I hope u can reply this on time