The rate of depreciation?

From: Mostro (mostro_at_adelphia.netnospam)
Date: 12/05/04 

Date: Sun, 5 Dec 2004 12:08:24 -0500

 I am looking for help with the following problem. Does anyone have the
below book? I am having a hard time finding depreciation resources on the
web.

Thanks in advance...

 Application 5.2

1. Depreciation The rate of depreciation dV/dt of a machine is inversely
proportional to the square of where V is the value of the machine t years
after it is purchased. The initial value of the machine is $500,000. By the
end of the first year, the value of the machine decreases $100,000. Estimate
its value after 4 years.

Brief Calculus: An Applied Worktext, First Edition
Ron Larson - The Pennsylvania State University, The Behrend College
Bruce H. Edwards - University of Florida