Intra group sale – Cost of sales

Hello, I have some problems in answering Perkins from March June 2018 sample exam.

The question required candidates to remove the effect of subsidiary from the consolidated financial statement. However, I have some problems in arriving at cost of sales figure.

The scheme answer deducting $4400 (6600 x 8/12) without adding back intra group cost of sales.
The explanation for this is cost of sales is only needed to be adjusted in subsidiary’s individual financial statement. I could understand why would we do that.

However, in arriving the figure at consolidate company financial statement, group does not include all 8 months of $6600. Doesn’t the figure include in consolidated financial statement is $3400 (6600*8/12 and remove $1000 from the intra cost of sales for subsidiary ). Therefore the adjustment should be made for intra group sales as 6600 is not adjusted yet for intra cost of sales.

Here’s summary that I hope someone understand why i am so confused about this answer:

Let say x = company’s cost of sales

The consolidate cost of sales is 23980.
The calculation behind this is x + (6600 x 8/12) -1000 = 23980
Therefore x = 20580.

However, the scheme provide the answer as $19580, as it did not add back the 1000 intra group.

I really hope someone could clarify me this T.T