2006 New York Code - Sum Certain.

 
  Section 3--106. Sum Certain.
    (1) The sum payable is a sum certain even though it is to be paid
         (a) with a stated rate of interest or by stated installments; or
         (b) with  stated  different  rates  of  interest before and after
             default or a specified date; or
         (c) with a stated discount or addition if paid  before  or  after
             the date fixed for payment; or
         (d) with exchange or less exchange, whether at a fixed rate or at
             the current rate; or
         (e) with  costs  of  collection or an attorney's fee or both upon
             default.
    (2) For the purposes of subsection one of this section "a stated  rate
  of  interest"  shall  also  include  a  rate  of interest that cannot be
  calculated by looking only  to  the  instrument  but  which  is  readily
  ascertainable  by  a reference in the instrument to a published statute,
  regulation, rule of court, generally accepted  commercial  or  financial
  index,  compendium  of  interest  rates,  or  announced  rate of a named
  financial institution.
    (3) Nothing in this section shall validate any term which is otherwise
  illegal.