One partner bids 4C to ask inquire about the aces partner has.
Responder shows the cheapest ace, bidding 4NT to show the club ace: and 5C to show no aces.
Partner may make a follow-up bid of 5C to inquire into the number of aces. Responder then bids
5D = 1 ace
5H = 2 ace
5S = 3 aces
After a 4S response to 4C, a 5C bid may be used as a cue bid. Responder then cue bids the suit with his/her cheapest king.