A hospital purchases an x-ray machine for $20,000. The hospital expects the useful life of the machine to be 8 years, at which time its value will have depreciated to $3,000. The annual deprectiation rate, r (in decimal form)
is given by the formula below where n is the useful life of the item (in years), S is the salvage value in dollars),
and C is the original cost (in dollars). What annual depreciation ratie did the hospital use
r=1-(3)