Let us see what happened. 2
♦ was not alerted: that's MI.
West bid 2
♠ in a pre-balancing situation. Not as dangerous a bid as it looks, though not as safe as some auctions since North could have quite a fair hand.
Suppose West had known 2
♦ was an artificial game force: would he have bid 2
♠? No. He might have bid 1
♠ the previous round and did not, so why should he bid 2
♠ now?
If West passes, I see no reason for North or East to bid, so I would rule it back to 2
♦ making …? I look at the OP to find the jurisdiction – not given. 11 tricks is unlikely – probably needs a diamond lead. 10 tricks quite normal on say a heart lead, two rounds of diamonds, four rounds of hearts. Of course 9 tricks also quite likely. Let us weight the number of tricks under Law 12C1C, or give 9 tricks under Law 12C1E.
But this is for N/S: how about Law 12C1B? What about East’s double and West’s duck? [Double duck with rice: a lovely Chinese meal!
] Are these SEWoG?
The problem with the double is that it is based on a pre-balancing 2
♠. At the time East made it he was still misinformed. Of course, 3NT is cold off, so it is difficult to describe it as wild or gambling or a serious error.
How about the duck? It is not wild, nor gambling. But a serious error [unrelated to the infraction] [SEUTTI?]? East might sensibly have doubled with Kxx and an entry, so no, I do not believe it is SEUTTI.
So, Law 12C1C for both sides:
.. 10% of 2D +3, NS +150
+ 50% of 2D +2, NS +130
+ 40% of 2D +1, NS +110
Law 12C1E for both sides:
2D +1, NS +110, both at all probable and likely