The 4NT bid shows either:

1. 3 aces, or
2. 2 aces and a king of a genuine suit bid by the partnership

The responses to 4NT are:

1. 5NT with either * 2 aces * 1 ace and all the kings of the genuine suits bid by the partnership
2. 5 of the lowest genuine suit bid by the partnership with * no ace
3. 5 of a suit or a jump to the lowest genuine suit bid with * 1 ace

Responder may use his/her judgment when the response may have taken them over the agreed trump suit-- responder may invent a lower suit bid.

If responder holds 2 aces and a king, responder should be interested in a grand slam. Responder may bid the suit with the king and then make a constructive bid later.