Negotiable Instruments Law
Section 2. Certainly as to sum ; what constitutes.-The sum payable sum is a sum certain within the meaning of this Act, although it is to be paid-
(a) With interest; or
(b) By stated installments or
(c) By stated installments, with a provision that upon default in payment of any installment or of interest the whole shall become due; or
(d) With exchange, whether at a fixed rate or at the current rate; or
(e) With costs of collection or an attorney's fee, in case payment shall not be made at maturity.