Idiosyncratic Manual Bill Cancellation

If a bill's account is associated with a Customer Class that has a Cancel Bill algorithm, the system invokes this algorithm before the bill is displayed to determine if the bill is "cancellable". If the algorithm indicates the bill is cancellable, a button appears on Bill - Main. When clicked, the Cancel Bill algorithm is invoked again to cancel the bill. This functionality is meant to support unique cancellation needs required by some implementations; the sample base-package algorithm is empty.