3.17. Depreciation. A farmer buys a new combine (used for harvesting crops) for $380,000. He assumes that the value of the combine will drop, or depreciate, at a constant rate, and that it will be worth $100,000 in ten years. (We will examine other depreciation methods in the Chapter 6 exercises.) Let V(t) represent the value of the combine t years after it was purchased. (a) Find an expression relating V to t. Then find an expression relating V to t. (b) What will the combine be worth after 7 years? (c) When will the value of the combine fall below $80,000 ? (d) Graph V for 0t20 and indicate on your graph the answers for parts (b) and (c). (e) This method of estimating the value of a used piece of equipment is called straight-line depreciation. Explain why this is a sensible name