An extreme hand.

East will open with a weak 2♥ (with great shape).

South with a strong hand has a choice between double with the aim of bidding ♠ s to show a very strong hand. Other choices like 1♠  and 4♠ could be perceived as weak.

Over double or 1♠ West will bid 4♥ , giving North a difficult decision  and will probably pass. Over 1♠ he is more likely to bid 4♠ as his hand is great in ♠ s.

Over 4♠ passed round to West, West will bid to the leval of fit (or law of total tricks) 5♥ which will either be passed out or N/S may bid 5♠ .

4♠ make by N/S and 5♥ makes by E/W

A difficult one.

Classic duplicate. The side that wins the auction at the right level will win.

West has a choice to open vulnerable with his poor 11HCPs or not. The K♥ is not worth a full 3HCPs. However he has a good opening bid in 1♦ followed by a 2♣.rebid. 

West opens

If West opens 1♦ North may overcall 1♠  East will overcall 2♥  and south will raise to 2♠ .

West will rebid 3♣ and East will bid 3♥ .

West and North pass.

North may pass and East will bid a preemptive 3♥ . 

South will find it difficult to double at this vulnerability.

West passes and North bids 2♠ 

East will not be able to overcall and everyone else will pass.

So 2♠  makes for North = +110

2♥ makes for South = -110

3♥ -1 = -100