RKCB

After partner opens with a preempt on level 3 (Poor Man’s Blackwood - PMBW) 

4♣(4♦ for ♣)    =    asking about KC (5 KC with OP's suit as trump):

1. level    =    minimum, can hold 1KC    ➤    4NT/5♦    =    sasking about 1KC

2. level    =    1KC + maximum

3. level    =    1KC + Queen of trumps

4. level    =    2KC    ➤    next bid asks about the Queen of trumps