New equipment was just purchased for $750,000. Estimated salvage in 10 years is $50,000. Calculate the depreciation and book value at the end of year 4 for each of the following methods:
a) GDS MACRS method with a recovery period of 10 years
b) 200% DB method with a recovery period of 10 years
c) ADS SL method as an alternative to MACRS with a recovery period of 10 years, with the half-year convention enforced.