DEPSL(<N price>, <N value>, <N life>, <N periods>)
 Computes depreciation of an item by straight-line method.
 Returns <expN> total depreciation over number of <periods>.

 <price> is the original purchase price.
 <value> is the anticipated resale value.
 <life>  is the expected life of item in time periods.
 <periods> is the number of time periods to date.

 * Depreciation of an item purchased for $10,000 over 6 months.
 * Anticipated resale value is $1,000.
 * Expected life of item is 5 years.
 * Time period is months, 5 years is 60 months.
 m_deprec = DEPSL(10000, 1000, 60, 6)
 * <life> and <periods> are both months

 * Depreciation of same item over 4 years.
 m_deprec = DEPSL( 10000, 1000, 5, 4)
 * <life> and <periods> are both years


             Placed in the Public Domain by Tom Rettig Assoc.