On Fri, 30 Mar 2007 06:32:03 -0700, KC wrote:

Thank you Ron. My main point was: the amount that I changed was very small,
only from +1 to -1 as comparied to other figures. Why did the result changed
so drastically.

Another query was that if the first payment / cost was zero, why did the
result be zero?

The first payment needs to be negative. 0 and 1 are not negative values.
--ron