South will pass and West will bid 1♦ 

North has to bid 1♥ as a double is likely (but not in this case) will bid 2♣ and he does not have a bid as 2♥ would show a strong hand >~17HCPs.

East will pass (some may bid 2♦ )nd south will bid 1♠ 

West wil bid 2♦  and North will bid 2♠ 

East will bid 3♦ 

South has a choice 3♠  and 4♠ . The hand is strong with the bidding the singleton ♦  and 5/5 shape. The hand is stronger than 8HCPs - if you use the Kaplan and Rubens hand evaluator it comes out at 9.7. North is sitting over the hand with values which is good. So reasonable justification for a 4♠ bid - that makes on this occassion.