(count-change 100)
292
Oh? My apologies.
An interesting challenge - in a similar vein to this thread (https://www.theswamp.org/index.php?topic=39082.0).
((100 . 17)(50 . 23) (20 . 0) (10 . 45) (5 . 33) (2 . 6))
which means, 100 = £1 and you ran out of 20p-s.(_givechange 67 '(50 10 5 2 1))
then say decrement the first list, to update whats inside of the pay desk.