A company uses a linear model to depreciate the value of one of their pieces of machinery. When the machine was 2 years old, the value was $4.500, and after 5 years the value was $1,800 a. The value drops $ per year b. When brand new, the value was $ c. The company plans to replace the piece of machinery when it has a value of $0. They will replace the piece of machinery after years.