"40 pages were revised once" - so how can 10 pages which were revised TWICE be from a group which was only revised ONCE?

Rates for having a manuscript typed at a certain typing service are $5 per page for the first time a page is typed and $3 per page each time a page is revised. If a certain manuscript has 100 pages, of which 40 were revised only once, 10 were revised twice, and the rest required no revisions, what was the total cost of having the manuscript typed?
(A) $430
(B) $620
(C) $650
(D) $680
(E) $770

For 100-40-10=50 pages only cost is 5$ per page for the first time page is typed - 50*5=250$;
For 40 pages the cost is: first time 5$ + 3$ of the first revision - 40*(5+3)=320$;
For 10 pages the cost is: first time 5$ + 3$ of the first revision + 3$ of the second revision - 10(5+3+3)=110$;

Total: 250+320+110=680$.

OR:
100*5+40*3+10(3+3)=500+120+60=680.

Answer: D.

Hope it's clear.
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I thought the the ones receiving 1st review include ones with no review and the ones receiving 2rd review include the one with 1st review and no review.

10*(5+3+3)+(40-10)*(5+3)+(100-40)*5 = 110+240+300 = 650

This is very tricky, and there is answer (C_ that fits my reasoning (650). Can some one please explain why my reasoning is not correct?

Total cost = 50 * (New) + 40 (New + Revision1) + 10 * (New + Revision1 + Revision2)

Total cost = 50 * 5 + 40 * (5+3) + 10 * (5+3+3)

= 250 + 320 + 110

= 680

Answer = D
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We are given that the manuscript has 100 pages, and, of those pages, 40 were revised once, 10 were revised twice, and the remaining 50 pages had no revisions.

Thus, the charge for the 50 pages that required no revisions was 50 x $5 = $250.

Next we can determine the total charge for the 40 pages that were revised once. We have an initial charge of $5 per page and an extra charge of $3 per page for the revision. Thus, the total cost was 40 x ($5 + $3) = 40 x $8 = $320.

Finally, we can determine the total cost for the 10 pages that were revised twice. We again have an initial charge of $5 and then a charge of $3 for each revision. Thus, the total cost was 10 x ($5 + $3 + $3) = 10 x $11 = $110.

Therefore, the total cost of all 100 pages is $250 + $320 + $110 = $680.

Answer: D
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My friends sorry but on this one I MUST object the English.

If a certain manuscript has 100 pages, of which 40 were revised only once, 10 were revised twice,

This sentence is open to interpretation, whether you consider that those 10 pages were revised twice in total, so ones on the first revision and again later or if you consider that those 10 were revised ones and then revised two more times, you will be correct.

Low standard Q coming from OG.

A detailed explanation can be found in this video:
https://www.youtube.com/watch?v=E2KEk2TjCN4

We want to separate the calculations as follows:
100 pages * ($5/page) = $500
40 pages * ($3/page) = $120
10 pages * ($3/page for first revision) * ($3/page for second revision) = $60

Total $680

Answer D
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The key is to understand the question.

Some may assume that the 10 pages that were revised twice are included in the 40 pages that were revised once. Therefore the costs of those 10 pages are calculated once (100*$5+40*$3+10*$3=$650).

But it is not true, because pages revised once and pages revised twice are mutually exclusive! Therefore the costs of the pages revised twice need to add another $3 per page (100*$5+40*$3+10*($3+$3)=$680).