3NT is apparently an offer to play, 4♣ is a "help suit slam try" showing a maximum of 11 8421-points in clubs, and 4♦ is a cuebid showing 7 or less 8421-points in clubs. So what on earth am I supposed to bid?
Hint to whoever thought this up: if 4♣ is not a cuebid, then a 4♦ cuebid can't deny a 4♣ cuebid.

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