Another case of approximation not always finding the correct generator

[Ingmar Dasseville]

Depending on the exact way the file is written (0 or avg in the sum term, avg:int or avg:Amount, ...), the line transfer(a,b,c) => 0 < c =< balance(a) & 0 < c =< -balance(b).

is generated incorrectly. Without that line (which can be evaluated in the input), there are no issues.