Ahospital purchases a $500,000 magnetic resonance imaging (mri) machine that has a useful life of 9 years. the salvage value at the end of 9 years is $77,000. (a) write a linear equation that describes the value y (in dollars) of the mri machine in terms of the time t (in years), 0 ≤ t ≤ 9. (b) find the value, in dollars, of the machine after 6 years. $ (c) find the time, in years, when the value of the equipment will be $140,000. (round your answer to two decimal places.) yr