Puritan Cement Products placed a new sand sifter into production 3 years ago. It had an installed cost of $100,000, a life of 5 years, and an anticipated salvage of $20,000. Book depreciation charges for the 3 years are $40,000, $24,000, and $14,000, respectively. 

a. Determine the book value after 3 years.  

b. If the sifter’s market value today is $20,000, determine the difference between current book value, market value, and the expected salvage if an asset was retained for 2 more years.
c. Determine the yearly depreciation rate dt (t=1, 2, 3) and total percentage of installed cost written off thus far