South will preempt with 6-9 and 6+♣ s

West has a choice - a double (problem with 2♠s) or probably better 3♦ 

Over 3♦ North will pass.

East will bid 3♥ 

South will pass, preempters bid once and only bid again over forcing bids by partner.

West will raise to 4♥ 

North will pass.

East may want to explore a slam, though the lack of a fit in ♦ s and only one first round control is not good. With extreme circulation, cue bidding could be a route, but the key card you need to find is either a singleton ♣  or K♣ in partners hand.

4N RKCB ask by East

West will respond 5♦ (using 1430 the RKCB - the best RKCB https://www.bridgewebs.com/lincolnhills/Blackwood%20RKC%201430.pdf) shows 3 or 0 will allow East to bid 6♥ or explore for 7 by bidding 5N asking for Ks. Here is Larry Cohen on https://www.larryco.com/bridge-articles/slam-bidding-rkc

If East bids 5NT you need to be clear with partner the responses. The choices are:

1. Bidding Ks below the trump suit, starting with the lowest one. (Useful for specific Ks)

2. 6♣ =0, 6♦ =1, 6♥ =2, 6♠ =3,

Here is a link to a discussion on the subject https://bridgewinners.com/forums/read/intermediate-forum/5nt-for-kings-after-4nt-rkcb/

Using Method 1, with no Ks you normally would bid 6 of the trump suit. But with the ♣ bid by South, West might bid 6♣, not to show K♣ s, but likely the similar 2nd round control of a singleton. This would allow East to bid 7♥ s that makes.

As always getting to a small slam will be good, getting to a grand slam will not score a lot more.